Transmission Tower Structure Research Articles

Numerical Study on the Mechanical Properties of Transmission Tower K-Joints under Cyclic Loading

During the vibration of a transmission tower, the joints will be subjected to a reciprocating load. To obtain the accurate state of the transmission tower under the load, the mechanical properties of the joints under the vibration load must be considered. In this paper, the mechanical properties of typical K-joints in transmission tower structures are studied by numerical simulation. The failure mode of the K-joint under cyclic loading is also analyzed. The mechanical properties of the K-joint are discussed from the aspects of hysteretic characteristics, stiffness degradation, energy dissipation capacity, and ductility evaluation, and the influencing factors are discussed. The results show that the failure mode of the K-joint is related to the bolt grade and steel strength. When analyzing K-joints, the moment-rotation hysteresis curve should be combined with the realistic parameters of joints to consider the hysteretic behavior of the K-joint. The results provide a theoretical reference for the accurate modeling of transmission towers.

A Short Review on Various Types Transmission Tower Structure and Its Design

A Short Review on Various Types Transmission Tower Structure and Its Design

Wind-Resistant Capacity Modeling for Electric Transmission Line Towers Using Kriging Surrogates and Its Application to Structural Fragility

Wind loading on a transmission tower structure is jointly influenced by the wind field, structural parameters, and the geo-spatial configuration of the transmission line. Considering the multi-parametric effect, this paper aims at developing a limit capacity model for transmission towers under strong winds. To this end, the limit capacity of the tower is expressed via two equivalent means: one is the limit wind speed as a function of the wind angle of attack and the span of transmission line; the other is a limit capacity surface with three fundamental wind load components as the principal axes. An adaptive kriging surrogate modeling is constructed to approximate the function/surface with structural uncertainties considered. The performance of the surrogate model is improved by adding support points and then evaluated by the overall accuracy validation and local error check. A numerical example demonstrating the feasibility of the surrogate modeling for the limit capacity of the transmission tower under winds is presented. Finally, a fragility assessment concerning a practical transmission line and towers subjected to typhoons is accomplished using the established limit capacity model of the tower.

Artificial Neural Network Plan for Transmission Tower Structure Safety Assessment

The security of transmission tower structure is the foundation to ensure the safe operation of power grid. The research of fuzzy qualitative assessment method for the structural health of transmission towers is the basic work of large-scale digital power grid engineering. In this paper, artificial neural network (ANN) is used as a generalized tool for structural health assessment of transmission towers. The feasibility of using artificial neural network to qualitatively evaluate the structural health of transmission towers is verified by numerical simulation data. In order to train the artificial neural network, the displacement, stress and other signals generated by the finite element model are calculated and used as the training input of the artificial neural network. The detailed stress results of the finite element model are calculated as the qualitative evaluation basis of the structural health, and the training output of the artificial neural network is generated. By the same method, the test set is generated, and it is found that the artificial neural network is feasible for the fuzzy qualitative assessment of the structural health of transmission tower, and the misstatement rate is less than 5%.

Damage Detection of Transmission Tower Based on Stochastic Subspace and Statistic Model

During the long service period of the transmission tower, the severe environment, material aging and fatigue effects result in the damage accumulation and resistance fading of the transmission tower, which even lead to the structural failure. In this paper, a stochastic subspace-based damage detection algorithm combined with statistical model is proposed for the damage identification of transmission tower structures through processing and analysing its vibration signals. Based on the structural modal parameters identified from the structural vibration response, the nominal modal parameters are defined. Considering that the Hankel matrixes constructed by the system observability matrix and the system output covariance matrix have the same kernel space, the damage index sensitive to the modal parameters is constructed. In the manuscript, firstly, the damage index establishment method and process of the algorithm are presented; and then the vibration data of transmission tower structure simulation under different damage conditions are obtained through numerical simulations; finally, above data are analysed to obtain the damage identification results of transmission tower. The results show that the method proposed in this work can effectively identify the local damage of transmission tower structure.

Analyzing the Limit Loading of Transmission Tower by Means of Finite Element Model

The truss structure has been widely used in the area of high-voltage electric power transmission due to its limited mass and great stiffness. The carrying capacity should be known in advance before the practical usage of transmission tower. As a result, analyzing the limit loading of transmission tower can be significantly useful. In this research, a model of transmission tower structure has been established by a software named Abaqus 6.14. By imposing different loading forces to the finite element model, the locations of limit stress and displacement were figured out. It has shown that the truss structure in this article can bear no more than 198 kN of loading. Stresses meanly distribute in the two side of the tower body, decreasing with the increasing height. The limit stress shows up at the bottom and is at same side of loading force. Stress and displacement responses fit Hooke’s law perfectly, in other words, the proposed finite element model can be used in the design of transmission tower in practice.

Impact of First Tower Earthing Resistance on Fast Front Back-Flashover in a 66 kV Transmission System

Lightning stroke on a transmission tower structure is one of the major reasons that results in high voltages at the tower arms due to the excessive lightning current flowing through the transmission tower to earth. The Surge voltage seen at the tower cross arm on the first tower close to a substation is the worst case. If this voltage is higher than the withstand level of the insulator string, the insulation of substation equipment will be exposed to transient over-voltage called fast front back-flashover (FFBF). The peak of this transient overvoltage is affected by the value of the system’s earthing resistance. This paper studies the effect of reducing the grounding resistance of both the surge arrestor (SA) and the first transmission line tower adjacent to a 66 kV substation on FFBF. Three case studies using PSCAD/EMTDC software are presented to simulate the variation of the potential sire at the substation equipment with different resistance values for the first tower and SA earthing resistance. The paper also addresses the economic protection system for solving the problem of transient overvoltage. The study proves that the proper design of the first tower grounding system enhances the safety of the system and reduces the cost for the grounding system to the minimum.

Multi-scale Modelling and Wind-induced Vibration Analysis of Transmission Tower Structure

Based on the theory of node displacement compatibility, the multi-point constraint equations of beam-solid elements are derived. The beam element model and multi-scale model are established to analyze the wind-induced vibration response of the transmission tower. The analysis results demonstrate that the dynamic response of the two models is similar in the elastic stage, but the response of the multi-scale model is larger than that of the beam element model in the plastic stage. The main reason is that the multi-scale model can consider the stiffness degradation and cracking of the angle cleat, which will in turn influence the mechanical performance and failure mode of the structure.

Experimental Research of Mechanical Behaviour of GFRP Cross Arm of 500kV Transmission Tower

Glass fibre reinforced polymer (GFRP) material is used in the field of transmission tower structure because of its excellent electrical and structural performance. In this paper, a full scale GFRP composite cross arm of 500kV transmission tower is designed and a triaxial load-unload experiment is conducted to study the mechanical properties of it. Three kinds of the most unfavourable load cases of GFRP cross arm are loaded, and the strain changes of the upper, middle and lower parts of the cross arm are obtained. It is verified that the bearing capacity of GFRP cross arm meet the design requirements and GFRP cross arm can be used safely in the transmission tower engineering.

Analytical and Experimental Modal Analysis of Electrical Transmission Tower to Study the Dynamic Characteristics and Behaviors

Experimental modal analysis of electrical transmission tower has been a challenging task for transmission tower researchers and design engineers in industry all over the world. Requirement of large numbers of sensors and accelerometers have been major constrain. In this study an innovative approach has been developed to investigate the dynamic characteristics and behavior of tower structure through analytical and experimental modal analysis. Firstly, a scale down (1:15) prototype model of transmission tower structure has been constructed with mild steel straps, joint together by welding, for modal testing. Modal hammer test has been conducted on the prototype tower model for extracting modal parameters; modal frequency, modal damping and modes, of the tower model which representing the actual tower structure. Secondly, the transmission tower structure has been modeled in standard finite element tools and analyzed analytically for natural frequencies. The first six natural frequencies and corresponding mode shapes have been determined analytically and first six natural frequencies have also been determined experimentally and compared with each other. The first six natural frequencies are determined analytically, the frequency range of 2–9 Hz has been found. The analytical and experimental modal analysis of transmission tower structure has been found to be in correlation with some differences. The maximum natural frequencies percentage difference 11.1% has been found; between the scale down model and the stand software model. Additionally, the tower structure has been modified and optimized to improve the stiffness of the diaphragm as per specification and practical limitations. The first order natural frequency of the modified tower has been reduced to 2.171 Hz from the 2.1773 Hz.

Identification of Structural Damage to Transmission Tower Structure Based on Dynamic Fingerprinting and Bayes Data Fusion

Identification of Structural Damage to Transmission Tower Structure Based on Dynamic Fingerprinting and Bayes Data Fusion

In-situ retrofit strategy for transmission tower structure members using light-weight steel casings

A practical technique to increase the robustness of existing light truss electric power transmission towers by restraining the buckling of their critical members is presented in this paper. Such buckling-critical members are enclosed by a tight-fitting rectangular casing comprised of two identical light gauge steel C- or U-shapes connected using screws. The steel casing was designed to postpone a decrease in the compression load-carrying capacity of the tower truss member by restraining its lateral-torsional and weak-axis buckling. Five full-scale restrained specimens and one unrestrained base-line specimen were manufactured and tested. One of the restrained specimens was loaded cyclically, while the other ones were tested under monotonic compression. Numerical models of the specimens were built by ABAQUS, and the simulation results were found to match the test observations. A parametric study was conducted using the validated numerical model to investigate the effect of the restraining casing thickness on the behavior of the restrained member. It was revealed that a steep drop in the compression capacity of the restrained member could not be substantially postponed when the thickness of the restraining casing was less than half of that of the restrained member legs. Conversely, the compression capacity of the restrained member could approach its yield strength in case that the thickness of restraining casing was set to be larger than 85% of that of the restrained member legs. The outcome of both experimental and numerical investigations demonstrates the feasibility of the proposed buckling restrainers for use in practice to enhance the mechanical robustness of light truss electric power transmission towers.

Cost Effective Design of Extra High Voltage Transmission Lines for Minimizing Transmission Congestion Problems

In Country like India having dense population, laying down new transmission lines is a great challenge. Also country being on fast track development mode, there is unceasing demand of electricity due to ever increasing industrialization. With advent of Extra and Ultra High Voltage transmission lines, corridor width for transmission lines can be reduced significantly. This paper describes utilization of a novel objective function for optimizing the structural design of Extra High Voltage transmission lines. Right of way for transmission lines are decided based on the effects of electromagnetic fields and corona effects in vicinity of the transmission lines. Objective function developed here takes into account the combined effects of electromagnetic fields to optimize design of transmission line tower structure. With compaction of towers further Right of way reduces leading to cost benefits in land procurement. A real time case of a transmission line situated in Gujarat is considered for validating the results of Optimization algorithm developed by authors. MATLAB has been used as programming platform for mathematical modeling as well as a platform for developing GUI that facilitates plotting of fields in vicinity of transmission lines in 2D and 3D environment. Genetic Algorithm coding is used to solve the optimization problem. Significant cost benefits and compactness in transmission tower structure is achievable as is clear from the results shown in this paper. This optimization algorithm can be extended for Ultra High Voltage lines also.

Buckling Analysis of Transmission Tower Considering Ice Load

Transmission lines are important lifeline projects. The stable operation of transmission lines is closely related to economic and social security and stability. Ice storm seriously affects the safety of transmission lines. The simulation analysis of ice damage of transmission tower structure has important theoretical significance and engineering value. In this paper, the finite element software ANSYS is used to analyze the buckling of the self-supporting tower based on eigenvalue buckling analysis and nonlinear buckling analysis. The effects of vertical span, uniform ice coating, uneven ice coating, and wind load were considered. The ice thickness of the tower buckling is reduced with the vertical span decreasing under uniform ice coating the transmission line. As the coefficient of unevenness increases, the thickness of the unstable ice coating of the tower drops sharply. The unstable wind speed decreases with the increase of ice thickness.

A Real-Time Reliable Condition Assessment System for 500kV Transmission Towers Based on Stress Measurement

Transmission power towers play an important role in power delivery systems. In recent years, some important results on reliability of transmission towers have been obtained based on theoretical analysis, but there are very few practical application systems of real-time condition monitoring. This paper proposes a new real-time reliable condition assessment system for 500kV transmission power towers based on stress measurement. The necessity of such systems and the architecture of the online monitoring system will first be presented. Through calculating the stress distribution condition of different components of the transmission tower under typical working conditions, those positions with relatively high failure probability in the transmission tower can be identified monitored for installing the stress sensors on them. A new method is presented for calculating the reliability index of the transmission tower structure is also developed based on the mechanical structure of the tower. In particular, the tower structure is simplified to a series system, and the Ditlevsen’s bounds is used to estimate the reliability of the tower system. Finally, a designed example for the online reliable condition assessment procedure is given using a 500kV oxytropis tower as an illustration.

PERILAKU STRUKTUR TOWER TRANSMISI TIPE SUSPENSION TERHADAP BEBAN ANGIN

The need for electricity supply in Indonesia is getting bigger along with the higher population growth. This gives encouragement to stakeholders to expand infrastructure development in the electricity sector. Nationally, the biggest demand for electricity is industrial sector, followed by household, business, and general sectors. In its application, the tower transmission structure has a major role to distribute the electricity needs in general. Transmission tower structure is classified as Truss structure. The truss frame is a structure consisting of a combination of rods forming triangular structures connected to each other, and encumbered in their joints. With the concept of balance of style and design of the existing code can be determined the capacity of tower and the response of the structure when carrying the primary loads, especially wind loads.

Study on Structure of Drum Type Transmission Tower Based on Modal Analysis

Based on the theory of dynamics, this paper takes a certain drum-type transmission tower as the research object, performs parametric modelling based on the actual size, and performs modal analysis on the tower structure through the finite element method. The frequency and mode of the first 20 steps of the transmission tower were extracted. The results of modal analysis show the dynamic characteristics and structural characteristics of the drum-type transmission tower, providing a theoretical basis and foundation for studying the earthquake resistance, wind resistance and other environmental incentives of the transmission tower structure.

Structural Mechanics Analysis and Safety Assessment of Transmission Tower

The safety of transmission tower structure is an important guarantee for the reliable operation of the transmission and distribution line. Furthermore, the perennial corrosion of steel components greatly weakened its ultimate bearing capacity, which is a huge detriment to the structural safety. Based on Analytic Hierarchy Process, the tower was divided into four layers and the components were classified into three categories. Corrosion allowance was used to define security index so that hierarchical and structural safety could be calculated.

Review on analysis and design of lattice steel structure of overhead transmission tower

Review on analysis and design of lattice steel structure of overhead transmission tower

Analysis of the seismic collapse of a high-rise power transmission tower structure

In this paper, an explicit dynamic analysis method is proposed to calculate the progressive collapse of a high-rise power transmission tower structure subjected to earthquake; the failure rule for member elements and the effect of different ground motion inputs and tower heights on the tower's collapse pattern in an earthquake are investigated. The study results show that explicit dynamic analysis can be easily applied to member fractures and that this method is suitable for calculating the seismic collapse of a power transmission tower. The selection of the member element failure rule has a significant impact on the forecast collapse pattern of a power transmission tower in an earthquake. The compression member buckling and softening failure rule, coupling the material nonlinearity with elastic buckling phenomenon, can stave off the effort in modeling the constructional eccentricities, which result in Euler buckling. For different earthquake waves, the high-rise power transmission tower demonstrates different collapse failure modes. The static collapse pattern from a pushover analysis and the dynamic collapse pattern are very different. The actual collapse pattern of a power transmission tower during the Wenchuan earthquake and the computer simulated collapse pattern are compared to validate the algorithm proposed in this paper. Finally, the seismic collapse vulnerability of a high-rise power transmission tower is evaluated based on probability estimate method.