Design Of Transmission Towers Research Articles

Collapse Analysis of a Transmission Tower-Line System Induced by Ice Shedding

Ice shedding causes transmission lines to vibrate violently, which induces a sharp increase in the longitudinal unbalanced tension of the lines, even resulting in the progressive collapse of transmission towers in serious cases, which is a common ice-based disaster for transmission tower-line systems. Based on the actual engineering characteristics of a 500 kV transmission line taken as the research object, a finite element model of a two-tower, three-line system is established by commercial ANSYS finite element software. In the modeling process, the uniform mode method is used to introduce the initial defects, and the collapse caused by ice shedding and its influencing parameters are systematically studied. The results show that the higher the ice-shedding height is, the greater the threat of ice shedding to the system; furthermore, the greater the span is, the shorter the insulator length and the greater the dynamic response of the line; the impact of ice shedding should be considered in the design of transmission towers.

ANFIS-Based Optimum Design of Real Power Transmission Towers with Size, Shape and Panel Design Variables using BBO Algorithm

The present study aims to provide a suitable approach to optimize transmission line towers with size, shape and panel design variables. MSTOWER software was used for modeling, analysis and design of the transmission tower. The design requirements applied to the structure were in accordance with ASCE10-97 standard. Transmission line towers are optimized in two ways. The first method combines Biogeography based Optimization (BBO) algorithm with MSTOWER software called BBO-MSTOWER and the second method, called BBO-ANFIS, uses an adaptive fuzzy neural inference system (ANFIS). To analyze the structure in the optimization process with the aim of reducing the computations and time of the optimization process. In order to evaluate the proposed method, two full-scale transmission towers were optimized as numerical models using the above two methods. Finally, the optimal design and time required in the two optimization methods were compared with each other as well as with the initial design of the tower and the results reported in previous studies. The results showed that with acceptable accuracy, ANFIS resulted in a significant reduction in the calculation time of the entire optimization process.

The effect of the thickness of steel pipe in linear and 2-dimensional stiffness analysis during design of transmission tower

Transmission towers are truss structures which are used to support the transmission power lines. It is important to design the transmission towers because unsuitable dimensions could waste the steel or lead to the failure of transmission towers. The thickness of the beam is a critical parameter during the design of transmission tower, which is directly related with the safety of the transmission tower. In this paper, a finite element method in linear and 2-dimension was employed to simulate the mechanical behaviour of transmission tower. Based on the calculated results, the variations of the maximum stress and the maximum displacement with the increasing thickness were displayed. Both the stress and displacement decrease dramatically with the increasing thickness and reach to a stable value if the thickness is beyond a critical thickness. When the thickness changes from 1 mm to 4 mm, the maximum stress and the maximum displacement decrease by 74%. When the thickness is more than 4 mm, the reduction of stress and displacement is not obvious. The percentage reduction of more than 70% is determined to be the criterion for optimum thickness. The relationships can be used in the design of the transmission tower.

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.

Design wind loads for transmission towers with cantilever cross-arms based on the inertial load method

Appropriate design wind loads can effectively avoid damage to transmission towers under strong wind and the wind-induced vibration coefficient β(z) is a critical parameter for determining those loads. Based on the inertial load approach, a step-by-step calculation method for the design wind loads of transmission towers considering the effects of cross-arms and diaphragms was proposed. In order to be consistent with actual transmission towers, the correction coefficient expressions of β(z), such as θb, θl and θη, considering the influence of local shape, mass and windshield area and the spatial correlation of the fluctuating wind, respectively, were derived and investigated. By the introduction of these three coefficients, the design wind loads for transmission towers with cross-arms and diaphragms can be determined. For transmission towers with cantilever cross-arms, design wind load formulae were derived, based on the analyses of 6 tower samples. The example of an actual transmission tower was used to verify the correctness of the derived formulae. The parameter analyses of the design wind loads showed that cross-arms have a great influence on β(z) and the wind-induced vibration response of transmission towers, but diaphragms only have a marginal influence and so may be neglected in the approximate calculation of the design wind loads. The research results provide a calculation method for the wind-resistant design of transmission towers.

Application Prospect of High Strength Aluminum Alloy in Transmission Tower

Transmission Towers are usually made of steel and protected from corrosion by hot dip galvanizing. This paper explores the application of high strength aluminum alloy to solve the problems of atmospheric corrosion of transmission tower in coastal area and heavy industry pollution area, sand erosion of zinc coating of transmission tower in strong wind sand area, and transportation difficulty in rugged mountain area. Compared with the traditional steel tower, the design and development of high-strength Aluminum Alloy transmission tower has remarkable characteristics. First, the high-strength Aluminum Alloy transmission tower does not need the traditional hot-dip galvanizing process of steel, which can reduce the pollution to the atmosphere and soil environment; Second, the density of Aluminum Alloy material is 1/3 of that of steel, which can reduce the difficulty of construction and reduce transport costs; third, high-strength Aluminum Alloy has good corrosion resistance, and there is no need for routine antiseptic maintenance as steel tower. The application of high strength aluminum alloy transmission tower in area with severe atmospheric corrosion, strong wind sand and mountainous area has high engineering application value.

Research on General Design and Application of Double-circuit T-Connection Tower In 110kV

Based on the investigation results and the current general design of state grid, this paper reasonably planned the design conditions of the tower. Taking the general design module as the basic tower type, a kind of double loop T-connection tower in 110kV with high generality was proposed, then carry out tower head planning and structural internal force analysis. Finally, the electric field finite element simulation is carried out to demonstrate the safety and reliability of the T-connection tower of cross arm arrangement. The tower can cover the T-connection conditions of 110kV double-circuit line in most areas of the country, and draw the tower diagram, which can be included in the general design of state grid transmission tower for reference of line designers. The cross arm of tower head is arranged in a crisscross way, which greatly simplifies the the double-loop T-connection scheme. One tower can replace the traditional multi-tower to complete the T-connection of the line, which reduces the cos t and occupation of land, also achieves good economic and environmental benefits.

Analysis and Design of Transmission Tower with Isolated Footing

A transmission tower is a tall structure, usually a steel lattice tower used to support an overhead power line. They are used in high voltage AC and DC systems. Steel tower structure resting on footings are currently becoming popular in any geographical location for electrical transmission, microwave transmission etc. It is necessary to have an understudy of the behavior of such structures and provide an economical design. To understand the performance of such high rise structures, it is necessary to know their behavior considering the soil structure interaction. Modeling of Transmission tower for the validation purpose is done. The basic soil properties of laterite were also found accordingly. Here the entire transmission tower with the isolated footing is modeled and analyzed in STAAD Pro V8i and STAAD Foundation software. The total load transmitted to each tower leg is found using STAAAD Pro and the size of isolated footing under each tower leg is determined using the STAAD Foundation software respectively. If required the soil structure interaction effects (SSI) can also be found easily

Stability analysis of glass fibre polyamide composite transmission tower

The cross-sectional degradation of steel transmission tower members due to corrosion has been one of the major issues in the transmission line system. The degradation of appearance of the material has also been seen because of corrosion. Therefore, there is a need for a less corrosive and high strength alternate material for transmission towers. It seems in recent years that alternate materials have been needed to replace steel which have low maintenance cost and good resistance to corrosion. The advantages of composite transmission towers are fire resistant, high stiffness, durability, high strength, moderate ductility, rigidity, easy to assemble and economical. The present study has made an effort to evaluate the performance of composite transmission tower. The glass fibre polyamide composite material has been used as a structural material. First, a finite element tower model of 132 KV has been set up in Structural Analysis and Design Software as glass fibre polyamide structural material as per transmission tower design guidelines (Code for Transmission tower design, IS 802.1.1.1995, Bureau of Indian Standards). Second, all the active loads like wind load on the body, wind load on conducting wires and ground wires, weight of conducting wires, weight of structure, weight of ground wires, weight of insulator and weight of line man with tools are calculated manually as per transmission tower design guidelines and applied in the finite element tower model. The stress distribution of the composite tower model has been simulated in Structural Analysis and Design Software and the results have been analysed. The broken wire condition (if one conductor is broken or earth wire is broken) has been innovatively considered in the present study. Results obtained in this article show that maximum induced stress on transmission tower member is less than the deign strength of glass fibre polyamide composite material. The glass fibre polyamide composite material has been found to be capable to withstand the maximum stresses induced due to different loading conditions considered in the study.

Modal parameters of a transmission tower considering the coupling effects between the tower and lines

The modal parameters of transmission tower-line systems constitute the basis of their wind and seismic design. However, such structures become complicated spatial systems due to the coupling effects between the towers and lines, making it difficult to evaluate the modal parameters of a transmission tower. To study the tower-line coupling effects on the frequencies and mode shapes of a tower, a stochastic subspace identification (SSI) method for identifying modal parameters is first introduced. Then, a finite element model of a transmission tower-line system is established, and the influences of three transmission line parameters, namely, the total span length, span ratio and height difference angle, on the modal parameters are analyzed. An aeroelastic model of the tower-line system is fabricated, and a percussion experiment is performed. The simulated and experimental results both show that the first-order frequency increases with an increase in the total span length but is only slightly affected by changes in the span ratio and the height difference angle. For the wind and seismic design of transmission towers, to obtain reliable natural vibration characteristics, a complete tower-line system model should be established instead of a single tower model.

Comparative Structural Analysis and Design of Transmission Tower and Monopole by using STAAD.Pro Software

Comparative Structural Analysis and Design of Transmission Tower and Monopole by using STAAD.Pro Software

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.

Experimental study on releasing the unbalanced tension using sliding suspension string with V‐shaped groove for transmission line under ice accretion

Unbalanced tension is one of the most important loads for the design of transmission towers under ice accretion in cold regions. A V-shaped sliding groove, which is a new type of connection for suspension strings, is developed as one of the most effective ways to release unbalanced tension. Eight typical experiments on the V-shaped sliding groove for releasing exceeding unbalanced tensions in transmission lines were designed and performed. The variation mechanism of unbalanced tensions was investigated, and the calculation theory of the critical sliding angle was verified. The experimental results showed that all specimens under all load cases could effectively simulate to release the unbalanced tension when the unbalanced tension increased to the critical value and the suspension string began to slide. Besides, the variation of conductor tensions for 100 m span could be simulated by adopting the curved orbit developed in this study, and the transmission-line parameters could be changed easily and the experiment became flexible. On the basis of the comparison of theoretical values with the test results of the conductor tension, the design method and practical use of the curved orbit were reasonable and feasible.

APPLICATION FEATURES OF POLY-CIRCUIT OVERHEAD TRANSMISSION LINES

It was shown the necessity to improve the operational reliability of overhead transmission lines as one of the main parts of the electric power transmission system. Question considered the feasibility of using poly-circuit overhead transmission lines. Analyzed the regulatory framework governing the design and construction of poly-circuit overhead transmission lines, as well as the calculation of electric and magnetic fields. It was shown that the regulatory framework governing nonrelevant to the possibility of using poly-circuit overhead transmission lines with a vertical arrangement of the phases wires. It was substantiated the advisability of additional in-depth studies of the electric and magnetic fields distribution of poly-circuit overhead transmission lines of various designs and voltage levels. It was presented the sequence of modeling the distribution of the electric field for overhead transmission line both traditional and poly-circuit design of 110 kV. It was presented the simulation results that confirm the accounting feasibility the design of transmission towers and the spatial arrangement of wires during the calculating of electric field strength. It was shown that simulation results using will significantly improve the reliability and operational safety of poly-circuit overhead transmission lines.

Experimental and numerical study of the axial stiffness of bolted joints in steel lattice transmission tower legs

Steel lattice transmission towers are constructed through the bolted assembly of various sizes of angle steel members and joint slip is inevitable; ignorance of this slip, which is the prevailing practice in transmission tower design engineering, can lead to an overestimation of the axial stiffness of bolted joints. This study investigates the impact of joint slip effects under tensile loading through a series of 30 tensile tests of 10 typical bolted joint configurations (3 specimens for each tested configuration) used in classic 500 kV lattice steel transmission line towers in China. Finite element analyses were also conducted as a complement and validation of concepts. Particular focus was placed on the load-deformation/slip curves of the tensile tests. The experimental results show that the joint slip was realized through a complicated process consisting of elastic deformation caused by the frictional load transfer and the asynchronous joint slip. Meanwhile, when subjected to an incremental axial tension, the axial stiffness of the bolted joints was highly nonlinear with regard to the elastic deformation. A simplified multi-linear strain-stress model was created using the experimental data to represent this nonlinearity in finite element analysis. The results from finite element analysis of the 30 tensile tests using this multi-linear strain-stress model show that the model can well predict the failure load level and positions of rupture of the angle members. The actual average axial stiffness of the tested bolted joints during the elastic deformation process of load transfer by bolt bearing is approximately 30% of the theoretical value. Finally, a general nodal element is proposed to describe the joint slippage effects and introduce this important factor in the structural analysis of lattice transmission towers in view of safer and more reliable design.

Optimization Design of Transmission Tower Based on Intelligent Selection

In this work, the optimal design method for self-supporting transmission tower is put forward, whose procedure is that the tower body form is selected intelligently firstly and then the members types of tower are chosen. The case base of towers is established with application of object-oriented technology. Then, the knowledge of tower body is mined out with case based reasoning and data mining technology. At the same time, the structural regulations of tower in the standard are merged into the knowledge base. So, the intelligent selection system of tower structural scheme based on case reasoning and data mining is explored. A 500kV self-supporting tower is optimized according to above method and a real model test is conducted. Comparison between optimal tower and original tower indicates that weight of optimal tower is decreased by 3% and its ultimate bearing capacity is increased by 19%. Statistical analysis results of 20 optimal towers indicates that the weight is average reduced by 4.7%, the components of the optimal tower are stressed more uniformly and bearing capacity of the tower is enhanced 12% at least.

Vibration Control Design and Test of Transmission Tower Using the Suspended Tuned Mass Damper

Vibration Control Design and Test of Transmission Tower Using the Suspended Tuned Mass Damper

Full-Scale Tests and Numerical Simulations of Failure Mechanism of Power Transmission Towers

Full-scale tests are conducted to investigate the load-bearing capacity and failure mechanism of power transmission towers subjected to various loading patterns (broken lines, wind and ice). Detailed finite element models of power transmission towers are established based on these experimental prototypes. To capture the member instability, the integral stability coefficients are obtained from different specifications and introduced into a user-defined material model. Subsequently, the failure analysis of power transmission towers is carried out using an explicit algorithm, and good agreement is found in comparison with experimental results. The results show that the proposed procedure is effective in simulating the power transmission tower failure process. The full-scale test and numerical simulation studies can provide a valuable database for the design of power transmission towers subjected to various loads.

Impact of wind loads on the resistance capacity of the transmission tower subjected to ground surface deformations

In this paper, two 1:2 scaled substructure models for a typical 110 kV transmission tower were designed and fabricated. The scaled tower substructure models were tested subjected to the stretching movements of horizontal ground surface under different wind load conditions. The wind speeds were assumed to be 15 m/s and 30 m/s, respectively in this study. The deformations of the tested tower models and the stresses and strains within the different members of the tower were fully measured. A large amount of the comprehensive test data was generated. Also a FE model using ANSYS was developed and validated by the test data. The research indicated that wind load has a significant unfavourable influence on the resistance of the transmission tower subjected to the ground surface deformation. Also the research showed that it is possible to use the FE model for the analysis and design of power transmission towers under ground surface movements.

Critical load cases for lattice transmission line structures subjected to downbursts: Economic implications for design of transmission lines

An extensive research program was recently conducted at The University of Western Ontario, Canada to investigate the load profiles that can be used in the analysis and the design of transmission towers subjected to downbursts. This research was motivated by many transmission line failures that have occurred in different locations around the globe during downburst events. It was also triggered by the fact that the existing codes of practice and guidelines provide very limited information regarding the critical load profiles associated with downbursts, which act on the towers and conductors of a transmission line system. One of the challenges in predicting the critical forces acting on the towers and conductors is that they are not only dependent on the magnitude of the event but also on its size and location relative to the center of the tower. This complexity results from the localized nature of such events. In the current study, an extensive parametric study is conducted on a number of transmission line systems to evaluate their critical response to downburst loads. The study considers the variations in the downburst location, angle of attack, and size to determine the effect of changing these parameters on the response of the transmission line systems. Based on the results obtained from this parametric study, three critical load cases are identified. The studied towers are then used to assess the economic impact of applying those load cases, expressed by the increase in the weight of the tower.