Iron tower safety assessment method and system based on failure mechanism

Abstract

The invention discloses an iron tower safety assessment method and system based on a failure mechanism, and relates to the technical field of power transmission and transformation, and the method comprises the steps: building a mechanical physical model of a power transmission iron tower based on the actual characteristic data of the power transmission iron tower measured by a data collection module; according to the mechanical and physical model of the power transmission tower, the damage mechanism of the power transmission tower under various operation conditions is analyzed; establishing an iron tower risk assessment system according to the damage mechanism of the power transmission iron tower under the multiple operation conditions and the stress state of each part of the power transmission iron tower under the multiple operation conditions; and if the risk assessment result of the iron tower risk assessment system on the power transmission iron tower indicates that the operation risk of the power transmission iron tower does not meet the preset risk requirement, performing global optimization on the power transmission iron tower under various operation conditions based on a multi-target global optimization algorithm so as to ensure that each part of the power transmission iron tower meets the strength safety requirement.

Description

Technical Field

[0001] The present application relates to the technical field of power transmission and transformation, and in particular to a method and system for evaluating the safety of an iron tower based on a damage mechanism. Background Art

[0002] The transmission network is a complex system composed of wires and transmission towers. In the context of large-scale transmission of electric energy in my country, many transmission lines must pass through various extreme geological and geomorphic areas. The operation of the transmission network is not only affected by internal factors of the system, but also by external environmental factors, such as natural disasters such as wind load, ice and snow, earthquakes, and geological disasters such as landslides, mudslides, collapses, and ground subsidence. These factors pose a serious threat to the safe operation of transmission lines.

[0003] Transmission towers are important equipment in overhead transmission lines. Over the years, the load has caused the transmission tower structure to accumulate damage, posing serious safety hazards. As a large-scale lifeline project, the damage of the transmission tower structure will lead to the paralysis of the power supply system and even cause fires and other serious consequences, not only causing significant economic losses, but also directly affecting the country's production and construction and people's living order.

[0004] Based on the above analysis, there is an urgent need for a tower safety assessment method based on damage mechanism to meet the needs of assessing the safety of transmission towers. Summary of the invention

[0005] The embodiments of the present application provide a tower safety assessment method and system based on a damage mechanism to solve the above-mentioned technical problems.

[0006] The present application provides a tower safety assessment method based on destruction mechanism, comprising: establishing a mechanical and physical model of the transmission tower based on actual characteristic data of the transmission tower measured by a data acquisition module; wherein the data acquisition module comprises a field data measurement unit and a weak component characteristic measurement unit; analyzing the destruction mechanism of the transmission tower under various operating conditions according to the mechanical and physical model of the transmission tower; simulating and displaying in real time the stress state of each part of the transmission tower under various operating conditions according to the mechanical and physical model of the transmission tower; establishing a tower risk assessment system according to the destruction mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions; if the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirement, performing global optimization on the transmission tower under various operating conditions based on a multi-objective global optimization algorithm to ensure that each part of the transmission tower meets the strength safety requirement.

[0007] The present application provides a tower safety assessment system based on a destruction mechanism, comprising: a mechanical and physical model establishment module, which is used to establish a mechanical and physical model of the transmission tower based on actual characteristic data of the transmission tower measured by a data acquisition module; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit; a destruction mechanism analysis module, which is used to analyze the destruction mechanism of the transmission tower under various operating conditions according to the mechanical and physical model of the transmission tower; and a real-time operation status assessment module, which is used to simulate and display the mechanical and physical model of the transmission tower in real time under various operating conditions. the stress state of each part of the transmission tower; the risk assessment module includes a risk assessment system establishment unit, which is used to establish a tower risk assessment system according to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions; a global optimization module is used to perform global optimization on the transmission tower under various operating conditions based on a multi-objective global optimization algorithm if the risk assessment result of the transmission tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirements, so as to ensure that each part of the transmission tower meets the strength safety requirements.

[0008] Based on the embodiment provided by the present application, a mechanical and physical model of the transmission tower is established based on actual characteristic data of the transmission tower measured by a data acquisition module; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit; according to the mechanical and physical model of the transmission tower, the destruction mechanism of the transmission tower under various operating conditions is analyzed; according to the mechanical and physical model of the transmission tower, the stress state of each part of the transmission tower under various operating conditions is simulated and displayed in real time; according to the destruction mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, a tower risk assessment system is established; if the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirements, the transmission tower under various operating conditions is globally optimized based on a multi-objective global optimization algorithm to ensure that each part of the transmission tower meets the strength safety requirements. Thereby, it can be used to support the construction, operation and maintenance of transmission towers and prevent serious accidents such as tower collapse. At the same time, the proposed safety assessment system combined with global optimization technical measures can greatly reduce the operation and maintenance costs of transmission lines, save manpower, improve the efficiency of operation and maintenance, and enhance the management level of transmission towers. It has very important theoretical significance and engineering application value for ensuring the safety of transmission lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings described herein are used to provide a further understanding of the embodiments of the present invention and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0010] Figure 1 is a flow chart of an optional tower safety assessment method based on a damage mechanism according to an embodiment of the present application;

[0011] Figure 2 is a structural diagram of an optional tower safety assessment system based on a damage mechanism according to an embodiment of the present application;

[0012] Figure 3 A schematic diagram of an optional technical route according to an embodiment of the present application;

[0013] Figure 4 is a flow chart of an optional finite element modeling algorithm according to an embodiment of the present application;

[0014] Figure 5 is a schematic diagram of an optional equilateral angle steel according to an embodiment of the present application;

[0015] Figure 6 A schematic diagram of an optional connection of models of different scales according to an embodiment of the present application;

[0016] Figure 7 It is a schematic diagram of an optional transmission tower condition assessment project according to an embodiment of the present application.

[0017] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0019] Transmission towers play an extremely important role in the transmission of electric energy. Their mechanical properties and structural strength directly affect the safe and economic operation of the entire power system. Therefore, continuous in-depth research on the safe operation of transmission towers in the line system, especially the overall stability of the towers themselves and the local bearing capacity, is of great scientific research significance and practical application value.

[0020] At present, some companies are operating transmission towers with old and weak structures and insufficient strength of local components, which leads to serious lack of bearing capacity. Under extreme weather conditions such as strong winds and icing, accidents such as tower collapse are very likely to occur, which seriously threatens the safe and stable operation of the power grid. In order to improve the safety and reliability of such towers, it is urgent to conduct in-depth research on their failure mechanisms. On this basis, it is also necessary to propose an effective risk assessment method for safe operation of towers, so as to grasp the health status and operation risks of transmission towers in real time, and then take effective reinforcement technical measures for the towers according to the results, so as to realize the normal operation of transmission lines under different working conditions.

[0021] Alternatively, if Figure 1 As shown, the present application provides a tower safety assessment method based on a damage mechanism, comprising:

[0022] S101, establishing a mechanical and physical model of the transmission tower based on actual characteristic data of the transmission tower measured by a data acquisition module; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit;

[0023] S102, analyzing the failure mechanism of the transmission tower under various operating conditions based on the mechanical and physical model of the transmission tower;

[0024] S103, based on the mechanical and physical model of the transmission tower, simulating and displaying in real time the stress state of each part of the transmission tower under various operating conditions;

[0025] S104, establishing a tower risk assessment system according to the failure mechanism of the transmission tower under various operating conditions and the stress state of various parts of the transmission tower under various operating conditions;

[0026] S105, if the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operation risk of the transmission tower does not meet the preset risk requirements, the transmission tower under various operating conditions is globally optimized based on a multi-objective global optimization algorithm to ensure that all parts of the transmission tower meet the strength safety requirements.

[0027] Based on the embodiment provided by the present application, a mechanical and physical model of the transmission tower is established based on actual characteristic data of the transmission tower measured by a data acquisition module; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit; according to the mechanical and physical model of the transmission tower, the failure mechanism of the transmission tower under various operating conditions is analyzed; according to the mechanical and physical model of the transmission tower, the stress state of each part of the transmission tower under various operating conditions is simulated and displayed in real time; according to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, a tower risk assessment system is established; if the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirement, the transmission tower under various operating conditions is globally optimized based on a multi-objective global optimization algorithm to ensure that each part of the transmission tower meets the strength safety requirements. Thereby, it can be used to support the construction, operation and maintenance of transmission towers and prevent serious accidents such as tower collapse. At the same time, the proposed safety assessment system combined with global optimization technical measures can greatly reduce the operation and maintenance costs of transmission lines, save manpower, improve the efficiency of operation and maintenance, and enhance the management level of transmission towers. It has very important theoretical significance and engineering application value for ensuring the safety of transmission lines.

[0028] Alternatively, if Figure 2 As shown, the present application provides a tower safety assessment system based on damage mechanism, comprising:

[0029] The mechanical and physical model building module 202 is used to build a mechanical and physical model of the transmission tower based on the actual characteristic data of the transmission tower measured by the data acquisition module 201; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit;

[0030] The transmission towers in this application may include but are not limited to 66 kV transmission towers, 110 kV transmission towers, and 220 kV transmission towers, etc. In the embodiments of this application, a 66 kV transmission tower is generally used as an example for description, and this application does not impose any restrictions on the voltage level of the transmission tower.

[0031] The research contents of this application mainly include the study of the damage mechanism of 66kV transmission towers based on structural stability theory, the study of the risk assessment method and risk assessment system for the operating status of 66kV transmission towers, and the study and demonstration application of tower reinforcement technical measures based on multi-objective global optimization methods.

[0032] Among them, the research on the failure mechanism of 66kV transmission tower based on structural stability theory: the tower model is established by using beam and rod units, the tensile performance and corresponding bearing capacity of each rod of 66kV transmission tower are studied, and the failure mode, stress distribution and plastic zone development of the rod under tension are analyzed. The main research focuses on the influence of the change of geometric parameters at the weak position of the structure on its force performance and bearing capacity. In-depth exploration of the precise mapping relationship between the state parameter data such as tower acceleration, dynamic strain, image information and the structural bearing capacity of each part of the tower, and based on the structural stability theory, the tower failure mechanism is revealed. 66kV transmission tower operation status risk assessment method: the performance degradation mechanism and state characteristic vector evolution trajectory of 66kV transmission tower in the whole life cycle are studied, and a 66kV transmission tower operation status time series prediction model based on finite element analysis and data-driven fusion is established, and then a 66kV transmission tower risk assessment system is developed to realize the real-time portrait and visualization of the health of the 66kV transmission tower, and then accurately quantify and assess the operation risk of 66kV transmission tower. Research and demonstration application of technical measures for tower reinforcement based on multi-objective global optimization method: According to the tower damage mechanism and operation status risk assessment results, considering the degree of safety factor compliance of the 66kV tower foundation, tower legs, tower body and tower head under different working conditions, the 66kV tower structure is globally optimized based on multi-objective global optimization methods such as non-dominated genetic algorithm. Based on this, technical measures for the reinforcement of 66kV transmission towers are proposed, such as adding additional rods and auxiliary materials at the optimized design location, and the effectiveness of the reinforcement measures is verified by taking actual projects as examples.

[0033] It should be understood that the finite element analysis method is a modern calculation method that has developed rapidly with the development of electronic computers. This application uses the finite element analysis method to model and calculate the mechanical properties and understand the failure mechanism and damage law of the transmission tower.

[0034] In the specific process of mechanical characteristics analysis of 66kV transmission tower, ANSYS software is used for modeling and calculation to improve the efficiency and accuracy of analysis. ANSYS software is a large-scale general finite element analysis software that integrates structure, fluid, electric field, magnetic field and acoustic field analysis. The mechanical characteristics analysis process of 66kV transmission tower based on ANSYS software includes pre-processing, load application and solution, and post-processing. The main task of pre-processing is to use the pre-processing module of the software to establish a finite element model of the 66kV transmission tower. It is the beginning of the analysis, including six basic steps: analysis preparation, setting unit type, setting real constants, defining material properties, creating models and dividing unit grids. The main task of applying loads and solving is to use the analysis and calculation module of the software to calculate the 66kV transmission tower. The steps are applying load conditions, applying boundary conditions and solving. The main task of post-processing is to use the software's post-processing module to analyze the data and graphics obtained from the mechanical calculation of the 66kV transmission tower, such as deformation, stress, internal force, reaction force, etc., and to display equal displacement diagrams, equal stress diagrams, etc. in various ways through the graphical interface.

[0035] In order to analyze the dynamic characteristics of the 66kV transmission tower, it is necessary to perform modal analysis on it, mainly including natural frequency and corresponding vibration mode analysis. This application uses the finite element analysis method to perform modal analysis on it. There are 7 methods for extracting its modal, namely, block Lanczos method, subspace iteration method, fast dynamic method, unsymmetric method, reduced method or condensed method, damping method, and QR damping method.

[0036] This application uses ANSYS finite element analysis software to perform modal analysis on 66kV transmission towers. The software can realize modal analysis of undamped and damped 66kV transmission tower structures and prestressed modal analysis. The elastic modulus (or some form of stiffness) and material density of the 66kV transmission tower structure must be specified in the modal analysis to provide the stiffness and mass required for the 66kV transmission tower structure analysis. For the 66kV transmission tower, a modal analysis of the undamped structure is adopted. The modal analysis process of the 66kV transmission tower can be: modeling, loading and solving, extended mode and result observation.

[0037] A damage mechanism analysis module 203 is used to analyze the damage mechanism of the transmission tower under various operating conditions according to the mechanical and physical model of the transmission tower;

[0038] The damage evolution of the 66kV transmission tower structure is an irreversible process of energy dissipation, which is accompanied by the conversion of heat and mechanical energy. From the perspective of thermodynamics, the damage variable of the transmission tower structure is from one internal state variable to another, which must satisfy the basic laws of thermodynamics: 1) The first law of thermodynamics, the law of conservation of energy, that is, the conservation property of energy transfer and conversion in all thermodynamic systems; 2) The second law of thermodynamics, which gives the directionality of energy transfer and conversion in all thermodynamic systems. For damage, it is accompanied by energy dissipation and is an irreversible thermodynamic process.

[0039] For the metal materials of 66kV transmission towers, under the action of load, the connecting components in the high stress area will undergo plastic deformation accompanied by damage evolution, that is, ductile damage of the material. This application adopts the Lemaitre damage evolution law to describe the plastic damage behavior of 66kV transmission towers. The Lemaitre model is a material damage model established within the framework of thermodynamics, which is suitable for describing the damage evolution of ductile materials such as 66kV transmission tower metals during plastic deformation. According to the Prandt l-Reuss flow law, it is believed that the total strain of the 66kV transmission tower in the plastic stage is the superposition of the elastic strain and the plastic stage strain. In the elastic stage, the strain still obeys the form of the generalized Hooke's law, and the plastic part strain is determined by the deviatoric stress tensor in an incremental form. According to the 66kV transmission tower structural strain equivalence principle, the strain generated by the damaged tower material under the action of effective stress is equivalent to the strain generated when the same material is intact.

[0040] During the operation of the 66kV transmission tower, the tower may be structurally damaged due to excessive local stress caused by the combined effect of various external loads and internal stresses. Therefore, it is necessary to analyze its stress and deformation under various conditions to ensure that its strength is safe enough. The damage forms of materials can generally be attributed to two types: brittle fracture and plastic yield. The materials of the tower are mostly steel, which belongs to plastic yield when damaged. At present, strength theory can be roughly divided into four types: maximum tensile stress theory, maximum tensile strain theory, maximum shear stress theory and distortion energy density theory. Among them, the maximum tensile stress and tensile strain theory are less used in actual engineering because their experimental results do not meet the requirements of most material properties; while the maximum shear stress theory and distortion energy density theory are consistent with the experimental results of most plastic materials. Therefore, this application uses this theory to perform mechanical analysis on the 66kV transmission tower.

[0041] There are many rods in the 66kV transmission tower, and the structural relationship between the rods is relatively complex. In addition, the nodes are rigidly connected. Therefore, the rods are subjected to the combined stress in multiple directions, and the exact value of the stress in the structure cannot be fully characterized by the conventional unidirectional stress. In order to accurately characterize the stress state of the tower, the von Mises stress is used to check the strength and stability of the tower. This stress can equate the stress of the material in a complex state to the stress in a unidirectional state. It follows the fourth strength theory of material mechanics, namely the distortion energy density theory. It believes that no matter what stress state the material is in, its yield is mainly caused by the distortion energy density, and it is believed that as long as the distortion energy density at the dangerous point reaches the distortion energy density of the material when it yields in unidirectional tension, the material will yield and fail. According to the fourth strength theory, the strength judgment condition calculation expression of the tower and the bracket is:

[0042]

[0043] Where: 1 , σ 2 , σ 3 are the principal stresses in three directions respectively; r4 is the equivalent stress of the fourth strength theory; [σ] is the allowable stress of the material.

[0044] A real-time operation status evaluation module 204 is used to simulate and display the stress status of various parts of the transmission tower under various operation conditions in real time according to the mechanical and physical model of the transmission tower;

[0045] The instability of 66kV transmission tower components mainly occurs in its most basic axial compression components, bending components and compression-bending components. It is very important to ensure that its components meet stability in the design and calculation of the tower structure. The instability problem of the transmission tower structure is divided into two types of instability: loss of local stability and loss of overall stability. Both will affect the normal load-bearing and use of the transmission tower components or structures, or cause other forms of structural damage.

[0046] (1) Factors affecting the overall stability of transmission tower structures

[0047] 1) The overall stability of the transmission tower structure design is not satisfied. The slenderness ratio of the transmission tower components (i.e. the ratio of the calculated length of the component to the radius of gyration of its cross section) is the most important factor affecting the overall stability of the structure. Special attention should be paid to the fact that the calculated lengths of the two main axis directions of the transmission tower component cross section may be different, and there will be a large difference between the actual support conditions at both ends of the component and its ideal support form. All support conditions cannot be generally idealized.

[0048] 2) Various initial defects of transmission tower components. There are usually various unpredictable or difficult to eliminate initial defects in transmission tower components, such as accidental eccentricity errors of axial compression components, residual stresses caused by hot rolling and cold working, welding residual stress deformation, etc. In the structural stability analysis of transmission towers, these defects seriously affect the ultimate bearing capacity of components.

[0049] 3) Changes in the stress conditions of transmission tower components. Changes in the load and use conditions of the transmission tower structure, such as node damage, unexpected impact loads, overloads, uneven foundation settlement, changes in the calculation diagram during the reinforcement of the transmission tower structure, etc., cause the stress of key transmission tower components to increase. In addition, changes in the force system often occur, such as the transformation of tension components into compression components, which leads to the overall instability of the transmission tower components.

[0050] (2) Factors affecting local instability of transmission tower components

[0051] 1) Local stability of transmission tower components is not satisfied. In transmission tower components, especially composite section components, when the local stability of the components does not meet the requirements specified in the specifications, such as the height-to-thickness ratio of the web of the I-beam section exceeds the limit, local instability is likely to occur.

[0052] 2) The reinforcement measures for the local stress-bearing parts of the transmission tower are unreasonable. For example, if no supporting stiffening ribs are set at the support or at the point of action of a large concentrated load, the external force is directly transmitted to the thinner web, which is more likely to cause local instability of these webs.

[0053] The risk assessment module 205 includes a risk assessment system establishment unit, which is used to establish a tower risk assessment system according to the damage mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions;

[0054] In some embodiments of the present application, the CRITIC method is used to evaluate the risk of 66kV transmission towers. The CRITIC method is an objective weighting method. Its basic idea is to establish objective weights of different indicators based on the comparison strength between different evaluation schemes within the same indicator and the correlation or conflict between evaluation indicators. The comparison strength of different evaluation schemes is characterized by standard deviation. The larger the standard deviation, the greater the difference in values ​​between the schemes. The correlation or conflict between evaluation indicators is a correlation analysis of the indicators. If the correlation coefficient of the two indicators is large, the information conflict of the two indicators is low. It can be seen that the CRITIC method can reflect the correlation and variability between the 66kV transmission tower data, can not only extract the information content of the indicators, but also can well solve the information redundancy problem caused by the correlation between different indicators. For the same section of 66kV transmission tower materials, the larger the standard deviation of the stress response change, the greater the amount of information contained in the tower structure state; and for different tower materials of the same tower, there must be a certain correlation between the mechanical responses of similar main material rods, and the greater the spatial distance, the smaller the correlation, so as indicators, their conflict is greater, and increasing their weights can retain more information on the tower material state.

[0055] The reliability of a 66kV transmission tower mainly depends on the reliability of the tower material with the highest utilization rate in the tower, and the tower material utilization rate is related to the bending and stress of the tower material. Therefore, by analyzing various indicators of tower materials under wind action and comprehensively considering the influence of different tower materials on the tower state, the wind-induced state and risk of the monitored tower can be evaluated.

[0056] The global optimization module 206 is used to perform global optimization of the transmission tower under various operating conditions based on a multi-objective global optimization algorithm if the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirements, so as to ensure that all parts of the transmission tower meet the strength safety requirements.

[0057] In one example, the overall technical route of this application is as follows: Figure 3 Based on the 66kV transmission tower health visualization and operation risk quantitative assessment system, this application can use a multi-objective non-dominated genetic algorithm to globally optimize the existing 66kV transmission towers in different states, ensuring that the tower foundation, tower legs, tower body and tower head meet the strength safety requirements, and then propose more reliable and reasonable reinforcement measures, so as to achieve the safe and stable operation of the 66kV transmission tower under different working conditions such as strong winds and icing.

[0058] Specifically, compared with the related art, the innovations of this application mainly lie in the following three points:

[0059] First, the relevant technology does not use the actual characteristic data of the transmission tower, that is, it does not consider the real characteristics of the weak component materials such as old and rusted and the loose connection nodes, and usually does not measure the wind speed, temperature, strain, inclination and other field data of the tower, resulting in low accuracy of the proposed tower model, and it is difficult to obtain the failure mechanism of the transmission tower under different operating conditions such as strong winds and icing. This application measures the material characteristics of weak components such as old and rusted and the loose connection nodes, and based on the field data of wind speed, temperature, strain, inclination, etc. measured by the existing 66kV transmission line monitoring device, establishes a refined mechanical and physical model of the 66kV transmission tower based on data-driven and finite element analysis methods, and then accurately describes the characteristics of the 66kV transmission tower under different operating conditions such as strong winds and icing, thereby providing support for the derivation of the failure mechanism of the 66kV transmission tower.

[0060] Secondly, the relevant technology does not propose a real-time operation status characterization system and risk assessment system for transmission towers serving the operation and maintenance of transmission lines. However, this application uses the proposed 66kV transmission tower mechanical and physical model based on data-driven and finite element analysis methods to simulate and display the precise stress status of each part of the 66kV transmission tower in real time in the terminal system, and then evaluates the operation risk of the 66kV transmission tower in real time in the terminal system, laying a theoretical and technical foundation for the transmission line operation and maintenance department to monitor the status of the 66kV transmission tower and ensure its safe operation.

[0061] Third, in the related art, the reinforcement measures of traditional transmission towers are generally aimed at only the weak components that have been discovered, and no more scientific and reasonable global reinforcement measures are proposed from a global perspective, which makes it difficult to ensure the safety of transmission towers under different operating conditions such as strong winds and icing. Based on the proposed 66kV transmission tower health visualization and operation risk quantitative assessment system, this application uses a multi-objective non-dominated genetic algorithm to globally optimize the 66kV transmission towers in different existing states, ensuring that the tower foundation, tower legs, tower body and tower head all meet the strength safety requirements, and then proposes more reliable and reasonable reinforcement measures, thereby achieving safe and stable operation of 66kV transmission towers under different conditions such as strong winds and icing.

[0062] Furthermore, the field data measurement unit is used to measure and obtain the field data of the transmission tower; wherein the field data includes wind speed, temperature, strain and inclination. The field data of the transmission tower can be measured by using the transmission line monitoring device;

[0063] The weak component characteristic measurement unit is used to measure the material characteristics of weak components and the loose characteristics of connection nodes; wherein the weak components include old components and rusted components.

[0064] In some embodiments of the present application, a mechanical and physical model of a 66kV transmission tower is established by using a finite element analysis method (or finite element theory) according to the following four steps:

[0065] Step 1: Use a mechanical testing machine with a maximum loading capacity greater than or equal to 250kN to measure the mechanical properties of the transmission iron connection nodes, corroded tower materials, old tower materials, and bolts, including elastic modulus, allowable stress, bending and shearing capacity, to provide accurate material property parameters for the construction of the transmission tower model and ensure the accuracy of the calculation results. Calculate the spatial position equation of the straight line where the main material is located according to the structural drawings of the transmission tower, list the spatial heights of the key points in each tower section, list the material properties and geometric cross-sections of each rod and define them;

[0066] Step 2: Use the spatial straight line equation of the main material and the spatial height of the relevant key points, and the symmetry of the structure itself to establish each key point, so that as the height increases, the key point number increases continuously and regularly; for the cross arm members, generate key points separately according to the drawings to establish the model;

[0067] Step 3: Taking advantage of APDL parameter modeling, define the cross-section positioning key points through parameter control, arrays, and loop statements, connect the key points of the bar with reference to the positions of the key points of the bar positioning, assign relevant attributes, and divide the grid, so that the spatial position of the angle steel is more realistic.

[0068] Step 4: Adjust the degrees of freedom of some structures according to the drawings, including releasing degrees of freedom and adding constraints; impose constraints on the tower legs on the numerical model to complete the pre-processing.

[0069] The finite element modeling algorithm flow chart used in this application is as follows Figure 4 As shown in the figure, h is the base tower height, hc is the subsequent design tower height, lc is the rod control parameter, and kc is the key point control parameter. The initial values ​​of the control parameters lc and kc are both 0. The values ​​are adjusted during the modeling process by the different h and hc parameters of the tower structure, so that the key point numbers show a continuous increase pattern, which is convenient for the establishment of rods and unit division in the later stage.

[0070] According to the above modeling process, by controlling the relevant parameters, the establishment of the same type of different height transmission tower structure models can be flexibly realized, which has good portability and convenience; and, for complex structural models, the use of APDL language is more suitable for model adjustment and analysis, so as to facilitate further in-depth research on the structure.

[0071] Furthermore, the damage mechanism analysis module includes:

[0072] The static characteristic analysis unit is used to analyze the static response of the transmission tower under various external load excitations; wherein the various external loads include accidental loads, variable loads, and permanent loads; accidental loads include earthquake loads, line break loads, and installation loads; variable loads include wind loads and ice loads; permanent loads include the deadweight of the transmission tower poles, ground wires, hardware, and insulators; the static response of the transmission tower under wind loads includes the wind loads acting on the transmission lines and the wind loads acting on the tower poles;

[0073] As a high-rise outdoor building system, the transmission tower line structure is subject to complex external loads. According to the different nature of the loads on the transmission line, it can be divided into accidental loads, variable loads, and permanent loads. Due to the influence of multiple loads and local extreme weather, tower collapse accidents are somewhat diverse.

[0074] The application of static wind load on 66kV transmission tower is mainly divided into two parts: 1) The wind load acting on the transmission line can be calculated according to the specifications and applied to the conductor and ground wire suspension points of the crossarm; 2) The wind load acting on the tower body can be calculated in sections according to the specifications and applied to the transmission tower based on the maximum wind speed in the area where the transmission tower is located.

[0075] According to the requirements of DL / T5154-2012 "Technical Specifications for Design of Overhead Transmission Line Towers", the wind load for transmission lines is calculated according to the formula:

[0076] W x =α·W 0 ·μ Z ·μ sc β c ·d·L p ·B 1 ·sin 2 θ

[0077] W 0 =V 2 / 1600

[0078] Among them, W x The standard value of horizontal wind load perpendicular to the conductor and ground line (kN); α is the wind pressure unevenness coefficient; W 0 is the standard value of the base wind pressure (kN / m 2 ) ; V is the wind speed at a reference height of 10m; μ z is the wind pressure height variation coefficient; μ sc The body coefficient of the conductor or ground wire: when the wire diameter is less than 17.0 mm or covered with ice (regardless of the wire diameter) μ sc All are 1.2, and the wire diameter is greater than or equal to 1.7mm;

[0079] μ scShould be 1.1; β c is the wind load adjustment factor for 500kV and 750kV line conductors and ground wires. For 110kV line, β c Take 1.0 for calculation; d is the outer diameter of the conductor or ground wire or the calculated radius when covered with ice. For split conductors, take the sum of the outer diameters of all sub-conductors; L P is the horizontal span of the tower; B 1 is the increased coefficient of wind load on conductors, ground wires and insulator strings covered with ice, and the values ​​for ice zones of 5.0mm, 10.0mm, 15.0mm, 20.0mm and above are 1.1, 1.2, 1.3, 1.5-2.0 respectively; θ is the angle between the wind direction and the direction of the conductor or ground wire (°).

[0080] According to the provisions of DL / T 5154-2012 "Technical Specifications for Design of Overhead Transmission Line Towers", the static wind load acting on the transmission tower is calculated according to formula (15):

[0081] W s =W 0 ·μ Z ·μ s ·B 2 ·A s β z

[0082] Where: W s is the standard value of tower wind load (kN); μ s B is the component shape coefficient, and the tower is calculated as 1.31+η, where η is the load reduction coefficient on the leeward side of the tower; 2 A is the wind load increase factor after the component is covered with ice. The value is 1.1 for 5.0 mm ice area, 1.2 for 10.0 mm ice area, 1.6 for 15.0 mm ice area, 1.8 for 20.0 mm ice area, and 2.0 to 2.5 for ice area above 20.0 mm. s The calculated value of the projected area of ​​the component subjected to wind pressure, without considering the inclination of the windward side of the tower, is calculated according to the filling coefficient φ = A s / A(Projected area of ​​wind pressure on the component A s The ratio of the fill factor to the component outline area A is obtained by multiplying the outline area by the fill factor to obtain the windward area A. s According to actual engineering experience, the tower head is densely arranged, so 0.3 is used for calculation, and the tower body is sparsely arranged, so 0.2 is generally used for calculation; β z It is the tower wind load adjustment coefficient. When the total height of the structure does not exceed 60m, the same coefficient is adopted for the structure height.

[0083] According to the current design specifications DL / T5154-2012 "Technical Regulations for Structural Design of Overhead Transmission Line Towers", GB50545-2010 "Design Specifications for 110kV~750kV Overhead Transmission Lines", and GB50017-2020 "Steel Structure Design Specifications", when the transmission tower structure is subjected to external loads, the main material rods are mainly subjected to the combined effects of axial pressure and bending moment. These rods may have insufficient local stiffness, strength, and instability, which may lead to damage to the transmission tower structure, and structural bearing capacity analysis is required.

[0084] The design specification of transmission towers DL / T5154-2012 "Technical Regulations for the Structural Design of Overhead Transmission Line Towers" adopts the method of limiting the slenderness ratio of components to ensure the stiffness of components. The slenderness ratio of components is calculated as follows;

[0085]

[0086] Among them, l 0 is the member length, r is the member radius of gyration, and [λ] is the allowable slenderness ratio.

[0087] The strength stress calculation formula of the main bending material is as follows:

[0088]

[0089] Where N is the tension or pressure value within the calculated component segment (N); A n is the net cross-sectional area of ​​the member (mm2); m is the member strength reduction factor, which is 0.85 for tension members and 0.70 for compression members; M x 、M y is the bending moment around the x-axis and y-axis at the same section; W x , W y is the cross-sectional resistance moment about the x-axis and the y-axis.

[0090] The stability calculation formula of the main material in the bending moment plane is:

[0091]

[0092] Where φ is the stability factor of the axially compressed member; m N is the reduction factor of the stable strength of the compression rod; A is the gross cross-sectional area of ​​the member; M is the maximum bending moment within the calculated member segment (N·m); W is the resistance moment in the section where the bending moment acts; N EX is a parameter, where λ x is the slenderness ratio of the component around the xx axis. The schematic diagram of the equilateral angle steel is as follows Figure 5 As shown, where B is the edge width and t is the edge thickness.

[0093] The dynamic characteristics analysis unit is used to analyze the dynamic response of the transmission tower under the excitation of various external loads.

[0094] For 66kV transmission towers, vibration instability is more likely to occur under dynamic external load excitation; modal analysis is the basis of dynamic characteristics analysis. The research object of this project is 66kV transmission towers, ignoring the influence of the overlap form between the transmission tower and the conductor. The results of modal analysis are independent of external loads and are only related to the structure of the structure itself. Through structural dynamic characteristics analysis, its main purpose is to find out the weak links of the structure itself and provide a certain reference for the subsequent reinforcement of the structure.

[0095] Further, the risk assessment system establishment unit establishes a tower risk assessment system according to the damage mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, and is configured as follows:

[0096] According to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, a structurally consistent multi-scale model of the transmission tower is established, and the performance degradation analysis and damage analysis of the structurally consistent multi-scale model are carried out throughout the life cycle to establish a tower operation state time series prediction model that integrates data and physics;

[0097] Determine the tower risk assessment system based on the tower operation status time series prediction model;

[0098] In order to study the risk assessment method of the operating status of 66kV transmission towers, it is necessary to understand the performance degradation mechanism of the towers and the evolution trajectory of the state characteristic vectors throughout the life cycle.

[0099] This application establishes a consistent multi-scale model of the 66kV transmission tower structure, performs performance degradation and damage analysis throughout its life cycle, understands its performance attenuation law, establishes a data-physics fusion tower operation status time series prediction model, and then develops a tower risk assessment system to achieve real-time portrait and visualization of the tower's health status, and accurately quantify and assess the tower's operating risk. Compared with the traditional single-scale model, the use of a multi-scale approach can not only consider the macroscopic performance of the structure, but also take into account local model information, more accurately determine the boundary conditions of the local model, and further consider the synergy of the two in the analysis of the tower's service process, and accurately realize the damage identification of the transmission tower material and the simulation of the failure process.

[0100] Consistent multi-scale model and damage analysis of transmission tower structure. In the simulation of multi-scale interface connection of transmission tower, the key is to consider the connection between various units and the interface connection between models of different scales, that is, the coupling between different scales; the interface coupling problem may involve the connection between units of different dimensions, such as beam units and solid units, shell units and solid units. Different unit models use different mechanical simplifications and assumptions, so it is necessary to adopt appropriate connection methods between models of different precision, so as to achieve force balance and deformation coordination without changing the degrees of freedom of different types of units on both sides of the interface, and avoid excessive constraints on the model. When the degrees of freedom of different types of units are the same, the connection can be achieved by using common nodes; when the degrees of freedom of different types of units are different, it is necessary to establish constraint equations to ensure the coordination of displacement and rotation between nodes. The connection of models of different scales is as follows: Figure 6 shown.

[0101] Typically, the constraint equations for interface coupling are expressed as:

[0102]

[0103] Among them, U(I) is the term of freedom; Coefficient(I) is the coefficient of the term of freedom U(I); N is the number of the term in the equation.

[0104] After the overall beam unit model of the transmission tower structure and the local microscopic solid model are established, the interface coupling method is used to couple the two into a multi-scale model. In ANSYS software, there are many ways to connect beam units and solid units across scales, including:

[0105] Interface constraint equation method: According to the connection characteristics of the nodes, the relationship between the degrees of freedom of the beam unit nodes and the solid unit nodes is established, that is, the node rotation degrees of freedom and displacement degrees of freedom. For three-dimensional units, six constraint equations are required.

[0106] Pseudo-beam method: The pseudo-beam method is to establish a "false beam unit" and insert it into the solid unit for a certain length. The length must span a solid unit, that is, the pseudo-beam unit should be connected to at least two nodes of the solid unit. The bending stiffness of the pseudo-beam can be set to infinity or about 1E4 times the stiffness of the actual beam unit.

[0107] MPC184 method: This method uses the MPC184 unit of ANSYS, which can be set as rigid rods, rigid beams, spherical constraints, universal joints, rotary joints and other motion joints. When the MPC184 unit is used as a rigid beam, the geometric entity and the beam line must share key points, forming the same effect as the "rigid arm" in structural mechanics.

[0108] Rigid domain method: This method generates rigid lines by selecting master nodes and slave nodes through constraint equations, and rigid lines with common nodes are connected as rigid surfaces or rigid bodies. The use of rigid domain does not require a common relationship between nodes and has good applicability.

[0109] Through consistent multi-scale model and damage analysis of the 66kV transmission tower structure, the performance degradation and damage laws of the entire life cycle are obtained, and a data-physical fusion tower operation status time series prediction model and a tower operation status and risk assessment method are established. Then, a transmission tower risk assessment system is developed to accurately quantify and assess the tower operation risk.

[0110] like Figure 7 As shown, the items assessed by the tower risk assessment system include tower foundation assessment items and transmission tower material assessment items; tower foundation assessment items include foundation surface damage and foundation surface exposure, deep burial of the guy wire foundation, foundation slope damage and foundation corrosion; transmission tower material assessment items include material, component stress, main material bending, component connection, inclination deformation and ancillary facilities.

[0111] Furthermore, the risk assessment system establishment unit establishes a structurally consistent multi-scale model of the transmission tower according to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, and is configured as follows:

[0112] According to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, the overall structural beam unit model of the transmission tower and the local microscopic solid model are established;

[0113] The interface coupling method is used to couple the overall structural beam unit model of the transmission tower and the local microscopic solid model into a structurally consistent multi-scale model of the transmission tower.

[0114] Furthermore, the risk assessment module also includes:

[0115] The operation risk quantitative assessment unit is used to quantitatively assess the operation risk of the transmission tower based on the established tower risk assessment system and provide a risk assessment report.

[0116] Further, the multi-objective global optimization algorithm includes one or more of the following algorithms: a gradient-based deterministic global optimization algorithm, an intuition- or experience-based random global optimization algorithm;

[0117] Among them, the deterministic global optimization algorithms include the filling function algorithm and the hole punching function algorithm; the random global optimization algorithms include the multi-objective non-dominated genetic algorithm and the simulated annealing algorithm.

[0118] The main idea of ​​the method using auxiliary functions such as filling functions and punching functions is to reach a point with a smaller function value from the current local minimum point by minimizing the function. The filling function method was first proposed by Ge Renfu and used to solve the global minimum point of multi-peak functions. Later, scholars such as Zhang Liansheng improved it. The basic idea of ​​the filling function method is to construct a filling function at the current local minimum point and minimize it, so that the current point reaches a point smaller than the current objective function value from the local minimum point of the original objective function. Compared with other global optimization algorithms, the advantage of the filling function method is that its idea is relatively simple and easy to construct, and it is also relatively easy to implement and verify numerically.

[0119] In some embodiments of the present application, a filling function method is used to achieve global optimization of a 66kV tower. The method of scalarizing a multi-objective problem is used to achieve multi-objective optimization of a 66kV tower. The basic idea is to use appropriate parameters to scalar the multi-objective problem and convert the multi-objective problem into a single-objective problem. Specifically, the multi-objective function is optimized by summing or multiplying by an evaluation coefficient, and then converted into a single-objective problem, which is then solved by the algorithm of the single-objective problem.

[0120] Furthermore, the tower safety assessment system based on the damage mechanism also includes:

[0121] The reinforcement measures recommendation module is used to determine the reinforcement measures for the transmission tower according to the global optimization results of the global optimization module. Among them, the reinforcement measures include reinforcing the original tower, building a new angle steel tower using the original foundation, re-building a new tower at a new site, adding auxiliary rods to some rods, reducing the calculated length of the main material to avoid local instability of the component and increasing the cross-sectional size of the structure, attaching and installing the reinforced components by bolt drilling, welding, etc., and the reinforcement locations are mostly the tower legs and the middle of the tower body.

[0122] The specific measures mainly include: using welding technology to cover the original main material with angle steel to achieve integrated strength improvement and reinforcement of the transmission tower; using different reinforcement measures for different rod parts and different material forms, such as adding prestressed cables, parallel components, removing bolts and replacing diagonal materials and auxiliary materials; according to the structural characteristics of angle steel transmission towers, studying the reinforcement method of bolt opening reinforcement of the main material of angle steel towers, and performing continuous welding around the reinforced angle steel to form a closed structure reinforcement; for old transmission towers, the tower legs are connected to the original leg components through cross connectors connected by bolts.

[0123] Furthermore, various parts of the transmission tower include the foundation, tower legs, tower body and tower head; and various operating conditions include high wind operating conditions and icing operating conditions.

[0124] It should be noted that in the present application, the embodiments implemented on the tower safety assessment system side based on the damage mechanism can be referenced with the embodiments implemented on the tower safety assessment method side based on the damage mechanism, and the present application will not describe them one by one.

[0125] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A tower safety assessment method based on damage mechanism, characterized in that: include: Based on the actual characteristic data of the transmission tower measured by the data acquisition module, a mechanical and physical model of the transmission tower is established; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit; According to the mechanical and physical model of the transmission tower, the failure mechanism of the transmission tower under various operating conditions is analyzed; According to the mechanical and physical model of the transmission tower, the stress state of each part of the transmission tower under various operating conditions is simulated and displayed in real time; Establishing a tower risk assessment system according to the failure mechanism of the transmission tower under various operating conditions and the stress state of various parts of the transmission tower under various operating conditions; If the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirements, the transmission tower under various operating conditions is globally optimized based on a multi-objective global optimization algorithm to ensure that all parts of the transmission tower meet the strength safety requirements.

2. A tower safety assessment system based on damage mechanism, the system implementing the tower safety assessment method based on damage mechanism as claimed in claim 1, characterized in that: include: A mechanical and physical model building module is used to build a mechanical and physical model of the transmission tower based on the actual characteristic data of the transmission tower measured by the data acquisition module; wherein the data acquisition module includes a field data measurement unit and a weak component characteristic measurement unit; A failure mechanism analysis module, used to analyze the failure mechanism of the transmission tower under various operating conditions according to the mechanical and physical model of the transmission tower; A real-time operation status evaluation module, used to simulate and display in real time the stress status of various parts of the transmission tower under various operating conditions according to the mechanical and physical model of the transmission tower; The risk assessment module includes a risk assessment system establishment unit, which is used to establish a tower risk assessment system according to the damage mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions; A global optimization module is used to perform global optimization of the transmission tower under various operating conditions based on a multi-objective global optimization algorithm if the risk assessment result of the transmission tower by the tower risk assessment system indicates that the operating risk of the transmission tower does not meet the preset risk requirements, so as to ensure that all parts of the transmission tower meet the strength safety requirements.

3. The tower safety assessment system based on damage mechanism according to claim 2 is characterized in that: The field data measurement unit is used to measure and obtain the field data of the transmission tower; wherein the field data includes wind speed, air temperature, strain and inclination; The weak component characteristic measurement unit is used to measure the material characteristics of the weak component and the looseness characteristics of the connection node; wherein the weak component includes old components and rusted components.

4. The tower safety assessment system based on damage mechanism according to claim 2 is characterized in that: The damage mechanism analysis module includes: A static characteristic analysis unit is used to analyze the static response of the transmission tower under the excitation of multiple external loads; wherein the multiple external loads include accidental loads, variable loads, and permanent loads; the accidental loads include earthquake loads, line break loads, and installation loads; the variable loads include wind loads and ice loads; the permanent loads include the deadweight of transmission tower rods, ground wires, hardware, and insulators; the static response of the transmission tower under wind loads includes wind loads acting on the transmission lines and wind loads acting on the tower rods; The dynamic characteristic analysis unit is used to analyze the dynamic response of the transmission tower under the excitation of various external force loads.

5. The tower safety assessment system based on damage mechanism according to claim 2 is characterized in that: The risk assessment system establishment unit establishes a tower risk assessment system according to the damage mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, and is configured as follows: Establishing a structurally consistent multi-scale model of the transmission tower according to the failure mechanism of the transmission tower under various operating conditions and the stress state of various parts of the transmission tower under various operating conditions; Performing full life cycle performance degradation analysis and damage analysis on the structural consistent multi-scale model to establish a tower operation status time series prediction model integrating data and physics; Determining the tower risk assessment system based on the tower operation status time series prediction model; Among them, the items assessed by the tower risk assessment system include tower foundation assessment items and transmission tower material assessment items; the tower foundation assessment items include foundation surface damage and foundation surface exposure, deep burial of the wire foundation, foundation slope damage and foundation corrosion; the transmission tower material assessment items include material, component stress, main material bending, component connection, inclination deformation and ancillary facilities.

6. The tower safety assessment system based on damage mechanism according to claim 5 is characterized in that: The risk assessment system establishment unit establishes a structurally consistent multi-scale model of the transmission tower according to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, and is configured as follows: According to the failure mechanism of the transmission tower under various operating conditions and the stress state of each part of the transmission tower under various operating conditions, a beam unit model of the overall structure of the transmission tower and a local microscopic solid model are established; An interface coupling method is used to couple the overall structural beam unit model of the transmission tower and the local microscopic solid model into a structurally consistent multi-scale model of the transmission tower.

7. The iron tower safety assessment system based on damage mechanism according to claim 2 is characterized in that: The risk assessment module also includes: The operation risk quantitative assessment unit is used to quantitatively assess the operation risk of the transmission tower according to the established tower risk assessment system and provide a risk assessment report.

8. The iron tower safety assessment system based on damage mechanism according to claim 2 is characterized in that: The multi-objective global optimization algorithm includes one or more of the following algorithms: a gradient-based deterministic global optimization algorithm, an intuition-based or experience-based random global optimization algorithm; Among them, the deterministic global optimization algorithm includes a filling function algorithm and a hole punching function algorithm; the random global optimization algorithm includes a multi-objective non-dominated genetic algorithm and a simulated annealing algorithm.

9. The iron tower safety assessment system based on the damage mechanism according to any one of claims 2 to 8, characterized in that: The tower safety assessment system based on the damage mechanism also includes: The reinforcement measures suggestion module is used to determine the reinforcement measures for the transmission tower according to the global optimization result of the global optimization module on the transmission tower; wherein the reinforcement measures include reinforcing the original pole tower, building a new angle steel tower using the original foundation, selecting a new site to rebuild a new tower, adding auxiliary rods to some rods, and increasing the cross-sectional size of the structure.

10. The iron tower safety assessment system based on the damage mechanism according to any one of claims 2 to 8, characterized in that: The various parts of the transmission tower include a foundation, tower legs, a tower body and a tower head; the multiple operating conditions include a strong wind operating condition and an icing operating condition.

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