Transmission Tower Research Articles

Wind-Induced Responses of Corroded Angle-Steel Transmission Tower

Corroded transmission towers, whose load-bearing capacities are lowered, are suffering from wind-induced damage. By simulating the member corrosion through section thinning, the structural dynamic finite element model of an angle-steel transmission tower with a corrosion depth of 0 mm to 1.4 mm was established using ANSYS/LS-DYNA software. The incremental dynamic analysis method was used to study the collapse mode of the tower under different degrees of corrosion, as well as the effects of corrosion on structural self-vibration characteristics, wind-induced member stress, and tower-top displacement. The results show that with the corrosion deepening, the first three vibration frequencies decrease, and the torsional mode becomes the first mode. When the corrosion depth is smaller, the overall structure failure occurs under strong wind. The failure starts at the most unfavorable oblique rod between the upper and middle cross arm, then expands to the rods under the lower cross arm. When the corrosion depth is larger, the overall structure failure occurs restrictedly between the upper and middle cross arm. Internal axial force and bending moment redistribution happen when corrosion deepens. Under the critical failure state, the oblique rods are always at a high stress level, while the stresses of the main rods decrease. Corrosion has a stronger impact on component strength and stability than on structural stiffness.

Influence of Woven Glass-Fibre Prepreg Orientation on the Flexural Properties of a Sustainable Composite Honeycomb Sandwich Panel for Structural Applications.

Owing to the high potential application need in the aerospace and structural industry for honeycomb sandwich composite, the study on the flexural behaviour of sandwich composite structure has attracted attention in recent decades. The excellent bending behaviour of sandwich composite structures is based on their facesheet (FS) and core materials. This research studied the effect of woven glass-fibre prepreg orientation on the honeycomb sandwich panel. A three-point bending flexural test was done as per ASTM C393 standard by applying a 5 kN load on different orientation angles of woven glass-fibre prepreg honeycomb sandwich panel: α = 0°, 45° and 90°. The results show that most of the sandwich panel has almost the same failure mode during the three-point bending test. Additionally, the α = 0° orientation angle shows a higher maximum load prior to the first failure occurrence compared to others due to higher flexibility but lower stiffness. In addition, the woven glass-fibre prepreg orientation angle, α = 0°, has the maximum stress and flexural modulus, which directly depend upon the maximum load value obtained during the flexural test. In addition, the experimental results and analytical prediction for honeycomb sandwich deflection show good agreement. According to the result obtained, it is revealed that woven glass-fibre honeycomb sandwich panels with an α = 0° orientation is a good alternative compared to 45° and 90°, especially when better bending application is the main purpose. The final result of this research can be applied to enhance the properties of glass-fibre-reinforced polymer composite (GFRPC) cross-arm and enhance the existing cross-arm used in high transmission towers.

Development and Application of Eddy Current Damping-Based Tuned Mass Damper for Wind-Induced Vibration Control of Transmission Tower

To reduce the low-order vibrations of high-voltage transmission towers in response to strong winds, a tuned mass damper (TMD) that uses eddy current damping (ECD) with omnidirectional damping function (ECD-TMD) is proposed here. Compared with previous similar devices, the outstanding advantage of the proposed ECD-TMD lies in its use of non-contact ECD, structural simplicity, lack of internal friction, ability to sense micro-vibrations, and in the asymmetric cantilever pendulum structure that enables omnidirectional vibration suppression. Aero-elastic model wind tunnel test and field measurements were used for analyzing and validating the vibration responses of a 50-m-tall transmission tower with and without the proposed ECD-TMD. The results demonstrated that the proposed ECD-TMD reduced transmission tower’s first-order bending vibrations along and across the direction of transmission line. For the mass ratio of approximately 2%, approximately 18–27% reduction of acceleration and 10–25% reduction of displacement occurred. Because the first-order resonance of the tower body in response to wind accounts for a small fraction of the background response, the addition of a TMD device suppresses structural wind vibrations in a limiter manner but can significantly increase the first-order bending damping ratio of the tower.

Research on Dynamic Characteristics Detection Method of Tall Power Transmission Tower

In addition to the gravity of the structure itself and the supported object, the open-air high-rise supported steel structure tower mainly bears dynamic loads. Take the transmission line tower as an example, such as wind load, conductor galloping, tower vibration and sudden unbalanced tension caused by line breaking. It is necessary to study the dynamic characteristic parameters to know the structural resistance to dynamic load. Therefore, from the perspective of dynamic safety evaluation, this paper designed the acquisition method of dynamic characteristic parameters and established a reliable finite element modal analysis model of transmission tower. Finally, the dynamic characteristic parameters such as natural frequency, vibration mode and amplitude of transmission line steel tower were obtained. It was found that the inclined material of the transmission tower might be unstable when the high-order natural frequency resonance occurred, which had important practical significance for structure design optimization and safety evaluation.

Conceptual Design of a Sustainable Bionanocomposite Bracket for a Transmission Tower’s Cross Arm Using a Hybrid Concurrent Engineering Approach

This research article elaborates on the conceptual design development of a sustainable bionanocomposite bracket for bracing installation in composite cross arm structures. The product design development employed the hybrid techniques of the theory of inventive problem solving (TRIZ), morphological chart, and analytic network process (ANP) methods. The current bracket design in the braced composite cross arm is composed of heavy and easy-to-rust steel material. Therefore, this research aims to develop a new bionanocomposite bracket design to replace the heavy and easy-to-rust steel bracket. This research also aims to implement a concurrent engineering approach for the conceptual design of bionanocomposite bracket installation to enhance the overall insulation performance. A preliminary process was implemented, which covered the relationship between the current problem of the design and design planning to build a proper direction to create a new design product using TRIZ. Later, the TRIZ inventive solution was selected based on the engineering contradiction matrix with specific design strategies. From the design strategies, the results were refined in a morphological chart to form several conceptual designs to select the ANP technique to systematically develop the final conceptual design of the bionanocomposite bracket for the cross arm component. The outcomes showed that Concept Design 1 scored the highest and ranked first among the four proposed designs. The challenges of the bionanocomposite bracket design for cross arm structures and the improvement criteria in concurrent engineering are also presented.

Prediction Framework of Vortex-Induced Vibration of Steel Tubes in Transmission Towers Based on Generalized Wake Oscillator Model

Steel tube members with high slenderness ratios in transmission towers are susceptible to vortex-induced vibration (VIV), which can lead to fatigue damage once the vibration amplitude exceeds a certain threshold. This study proposes a VIV prediction framework for transmission tower steel tube members with semi-rigid constraints, based on the developed generalized wake oscillator model (GWOM). Firstly, the GWOM is established by coupling the nonlinear Van der Pol oscillator with the Euler–Bernoulli beam equation and incorporating semi-rigid boundary conditions. Meanwhile, the identification methods for the rotational stiffness and empirical parameters in the GWOM are presented, respectively. Second, a numerical solution scheme of the GWOM is derived based on the central difference method, and then a VIV prediction framework for steel tube members with arbitrary structural configuration is established. Comparisons with published experiments demonstrate that the proposed GWOM-based prediction framework has a promising accuracy in estimating the lock-in range and maximum VIV amplitude. The influence of semi-rigid constraints on the VIV of steel tube members is mainly manifested in the critical wind speed, but it has little effect on the amplitude branch. The proposed framework provides an efficient and cost–effective alternative to traditional experimental methods and computational fluid dynamics CFD simulations for predicting the VIV of steel tube members in transmission towers.

In-situ live jacking technology of corner transmission tower

Aiming at the current situation that the foundation of the corner transmission tower is corroded, sunken, or the height of the tower line is insufficient, innovative low-cost technology is proposed to upgrade the foundation in-situ based on no power outages, and the analysis of the whole process of the in-situ live jacking construction of the transmission tower is studied in this paper. Firstly, through elastic mechanical equilibrium relationship, two form-finding methods of numerical analysis are derived and the results of several form-finding methods are analyzed and compared by a project example, among which the result error of the finite element method and the catenary method is negligible, while the error of the parabolic method is about 2% compared with the first two methods, but it can meet the engineering requirements. Secondly, the relevant laws of internal force and deformation of the lifting process are summarized, and a comparative analysis of theoretical and measured results verified the reliability and safety of the technology. Through the calculation program of the self-compiled parabolic method, the laws of tower line changes during the lifting process of the transmission tower are summarized, providing technical support for engineering practice and reference for related research.

Numerical and experimental investigation of a floating overhead power transmission system

A promising concept of floating offshore overhead power transmission system (FOPTS), in which the power transmission tower is installed on a TLP-type floating foundation, is investigated experimentally and numerically to study its feasibility. A numerical method is proposed in which the potential flow theory is used to evaluate the floating foundation hydrodynamics. The lumped-parameter method with a wake oscillator model is applied to the aerodynamic modelling of the overhead in order to determine the wind-induced motion and the corresponding internal force of the conductors. Multi-body simulations are performed in Simscape® by coupling the floating foundation hydrodynamics and the conductor aerodynamics. Wind-tunnel experiments on a simplified FOPTS model are carried out to study the coupled motion of the TLP tower and the overhead conductor. The proposed numerical method is validated by comparison of the conductor tension and motion to the experiment. Numerical simulations have been performed under realistic offshore environments based on the meteorological data of the Sea of Japan. Wind-wave misalignment effects on the structure of the FOPTS are investigated, and the safety of the conductors, the mooring lines, and the sea navigation are discussed.

The Bearing Capacity of Composite Insulated Cross Arm Tower under Typhoon Load

Typhoon meteorological disasters occur frequently, which seriously threaten the safe and stable operation of old transmission lines. The old transmission towers can be retrofitted with composite insulated cross arms to solve the problems of low capacity of wind protection design and insufficient distance between conductor and ground. The paper analyzes the wind load and bearing capacity of composite insulated cross-arm towers under the action of a typhoon through theoretical calculation and finite element analysis and puts forward the calculation method of wind load under the action of a typhoon, and it is revealed that typhoon has less influence on the force of composite cross arm and greater influence on the deformation of the composite cross-arm. Finally, the bearing capacity of a composite insulated cross-arm tower under typhoon load is proposed.

Design of rapid erection system for transmission lines for disaster rescue

The rapid erection system of transmission lines in disaster relief can restore the power supply in the disaster area in a very short time. It takes a long time to construct transmission lines in post-disaster relief and reconstruction. This paper designs the transmission line erection system with the idea of light quality and modularization and puts forward the dimensions and structures of auxiliary hoisting towers and overhead towers. Then, considering that the transmission line is a tall flexible structure, which is very sensitive to wind load, the finite element model of the transmission tower is established to analyze the simultaneous stress of the overhead tower and the lifting tower under extreme conditions. The study verifies the feasibility and stability of the designed transmission line rapid erection system.

INFLUENCE OF BOLTED SPLICE CONNECTIONS ON THE GLOBAL BEHAVIOUR OF STEEL LATTICE TELECOMMUNICATION TOWERS

The bolted joints in the leg and the bracing members of the lattice transmission towers are always subjected to predominant axial forces, which will cause joint slip that greatly affects the global be-haviour of the whole structure. The paper shows the results of the numerical modelling of the re-sponse of the steel lattice communication tower, with height h = 40.5 m located in Rzeszów. A comparison was made of five tower models, differing in the characteristics of the joint force-elongation relationship, including stiffness of the components and also joint slippage, coming from Category A joints. The paper presents the difference in displacements and rotations of chosen tower panels, internal forces in leg members, as well as in the fundamental flexural frequency obtained without considering the force-displacement characteristic and with four different ways of modelling of joints behaviour

Nonlinear stability analysis of high-strength steel cylindrical shells under global bending

Most of the current research in high-strength steel focuses on high-strength steel axial compression members, and the cross-section forms are mainly welded H-shaped sections and box sections. However, few studies focus on the mechanical behaviour of high-strength steel cylindrical shells in bending, especially the different failure characteristics with changing slenderness ratios have not been comprehensively studied. Many thin cylindrical shells with dominant loading conditions of global bending are normally in medium aspect ratios, and their thickness lies in an uncomfortable range with buckling behaviour affected by both imperfections and plasticity. The key common applications of these shells are turbine towers, transmission towers, tall silos and tubular piles.It is not easy to define the strength of these shells due to the difficulty to harmonise the different failure modes as the slenderness ratio of the member changes. This paper explores the load-bearing capacity of high-strength steel cylindrical shells with a yield strength of 690 MPa under global bending. The effects of residual stress, pre-buckling deformation and material plasticity on load-bearing capacity were investigated. Different failure characteristics were defined as the slenderness ratio is changed. The bearing capacity curves were obtained based on the method in the European Code for Design of Steel Structures EN1993-1-6(2007). The expressions of the parameters to describe the bearing capacity curves were proposed. It is hoped that the results will provide a scientific and useful reference for the design of high-strength steel cylindrical shells in medium length under global bending.

Hazards and Treatment of Collapsible Loess Foundation on Ultrahigh Voltage Transmission Lines

With the development of ultrahigh voltage transmission line construction in northwest China, an increasing number of overhead transmission lines are crossing the loess regions. Ensuring the stability of electricity transmission towers and mitigating the risk of collapse are crucial prerequisites for the construction of transmission lines. Taking the 750 kV demonstration electricity transmission line in Guanting–Lanzhou East as an example, representative loess samples were selected for compression and collapsing sensitivity tests. Four foundation treatment schemes were designed, and the wetting deformation characteristics were investigated through numerical simulation of the rainfall infiltration process. Corresponding optimisation schemes were proposed. The collapsing process was divided into four stages through laboratory collapsing tests. The relationship function between saturation and the Duncan–Chang model parameters of loess was established, which was introduced into the finite element model to consider the rainfall infiltration process. The analysis of the displacement field, and loess saturation field with time after rainfall infiltration for the four schemes showed that adding a lime-stabilised soil cushion layer and waterproof layer to the inclined column foundation had the best effect. Given that the design scheme needs to consider safety and economy, the thickness of the cushion layer was optimised, thereby reducing the use of lime-stabilised soil by 20%. Research findings provide meaningful guidance for the design of transmission tower foundations in loess areas.

Single-Wire Transmission Methods: Justification of a Single-Wire Resonant Power Transmission System

Electricity supply as well as the provision of other forms of resources is one of the foundations of efficient agriculture. However, due to the reduction in the number of people living in rural settlements, there have been a large number of power lines with considerable lengths supplying small loads, hence resulting in an increase in power supply efficiency. A single-wire power transmission is an option for reducing the capital cost of power line construction by utilizing fewer conductors and fittings and lighter power transmission towers while lowering operational expenses. This paper considers the possible methods for single-wire energy transmission via the analysis of information sources such as Yandex and Google search engines; Scopus and Google Scholar scientific databases; and Cyber Leninka, eLIBRARY.ru, Elsevier, Springer, IEEE Xplore, and IGI Global electronic libraries. The conducted review revealed four alternatives: a single-wire earth return (SWER) system, a single-wire balanced line (B-Line), resonant wireless power transmission (SWPT) system, and a resonant single-wire power transmission system. The latter is of particular interest due to the lack of comprehensive and detailed information describing this technology, although it has distinct characteristics because of the peculiarities of the resonant mode of operation. The paper provides a comprehensive review of all existing published materials on the topic of “resonant systems for the transmission of electrical energy along a single wire”. The study covers the history of development and the structure of this system; describes its features, advantages, and the problems of using it; and the experience and fields of its application.

Multi-Drone Optimal Mission Assignment and 3D Path Planning for Disaster Rescue

In a three-dimensional (3D) disaster rescue mission environment, multi-drone mission assignments and path planning are challenging. Aiming at this problem, a mission assignment method based on adaptive genetic algorithms (AGA) and a path planning method using sine–cosine particle swarm optimization (SCPSO) are proposed. First, an original 3D digital terrain model is constructed. Second, common threat sources in disaster rescue environments are modeled, including mountains, transmission towers, and severe weather. Third, a cost–revenue function that considers factors such as drone performance, demand for mission points, elevation cost, and threat sources, is formulated to assign missions to multiple drones. Fourth, an AGA is employed to realize the multi-drone mission assignment. To enhance convergence speed and optimize performance in finding the optimal solution, an AGA using both the roulette method and the elite retention method is proposed. Additionally, the parameters of the AGA are adjusted according to the changes in the fitness function. Furthermore, the improved circle algorithm is also used to preprocess the mission sequence for AGA. Finally, based on the sine–cosine function model, a SCPSO is proposed for planning the optimal flight path between adjacent task points. In addition, the inertia and acceleration coefficients of linear weights are designed for SCPSO so as to enhance its performance to escape the local minimum, explore the search space more thoroughly, and achieve the purpose of global optimization. A multitude of simulation experiments have demonstrated the validity of our method.

Effects of Ce-La rare earth microalloying on the microstructure and corrosion characteristics of Q420 high-strength steel

In the present study, the effects of rare earth alloys on the corrosion resistance of Q420 high-strength steel have been studied by performing the neutral salt spray test and the electrochemical test. The influence rules for rare earth microalloying on the improvement of the corrosion resistance of Q420 high-strength steel, were then clarified. The results showed that the addition of rare earth elements will improve the corrosion resistance of Q420 steel. The corrosion resistance of the 2# and 3# steel was found to be better than that of the 1# and 4# steel. This was related to the effect of rare earth alloys on the shape and size of the inclusion. With a further increase in the content of rare earth elements,a large-sized inclusion appeared in the steel. When the content of the rare earth element was 0.01 %, the number and size of the inclusions in the Q420 steel were the smallest, and the corrosion resistance of the Q420 steel was the best. The corrosion resistance of the high-strength steel for transmission towers can thus be effectively enhanced by controlling the amount of rare earth element addition.

Analysis of Electromagnetic Radiation of Mobile Base Stations Co-located with High-Voltage Transmission Towers

This paper presents the analysis of electromagnetic radiation of mobile base stations co-located with high-voltage transmission towers. Although the layout of power poles and towers is uniform and symmetrical, the electromagnetic field radiated to the outside world is asymmetric. Field measurements were conducted in different co-located base station scenarios, and the field strength results in both the vertical and horizontal directions were analyzed in depth. Then, the ray tracing simulation method was used to obtain the electromagnetic field distribution characteristics for the 5G base station co-located high-voltage tower. Finally, the specific absorption rate (SAR) was adopted to evaluate human exposure in co-located base station scenarios, and a physical area-based human exposure assessment method proposed. The obtained results can be useful for inspectors of mobile base stations co-located with high-voltage transmission towers to avoid or reduce the impact of electromagnetic radiation.

Probabilistic method for wind speed prediction and statistics distribution inference based on SHM data-driven

For wind-sensitive structures, such as long-span bridges, high-rise buildings, transmission towers, etc., the prediction of wind speed and its statistical distribution are vital steps in the design and operation stages. Specifically, wind speed prediction is directly related to the value of wind load in the next occurrence; the statistical distribution of wind speed has regular characteristics, which can represent the random characteristics of wind field. In this paper, a probabilistic prediction model of wind speed based on Bayes’ theorem is proposed and verified based on structural health monitoring (SHM) data. Firstly, the Gaussian process is derived and used as an a priori function in Bayes’ theorem. In addition, the influence of six covariance functions on the prediction performance are discussed, that is, squared exponential (SE), Matern-3/2 (MA-3/2), Matern-5/2 (MA-5/2), automatic relevance determination SE (ARDSE), ARDMA-3/2, and ARDMA-5/2. Secondly, the correlation between the next wind speed and the previous wind speed is discussed by using the moving window method. Finally, the parameters in the three wind speed probability distribution functions (PDF), that is, Gumbel distribution, Weibull distribution, Rayleigh distribution, are updated in real time by increasing the SHM data based on Bayes’ theorem.

Electromagnetic Ultrasonic Shear-Horizontal Wave to Detect Corrosion Defect of Flat Steel for Grounding Device of Transmission Pole Tower

Detecting defects in grounded flat steel is essential for ensuring the safety and reliability of transmission tower grounding devices. However, traditional inspection methods, such as physical excavation and verification, are costly and time-consuming. This paper proposes a corrosion defect detection method for flat steel transmission tower grounding devices based on electromagnetic ultrasonic SH waves. In addition, using commercial software, a three-dimensional finite element simulation model of grounded flat steel with simulated pitting corrosion defects is constructed. The specified displacements applied to multiple surface sources mimic the horizontal shear vibrations generated by the electromagnetic ultrasonic transducer on the surface of the grounded flat steel during actual inspection. A simulation was used to investigate the propagation and attenuation characteristics of shear-horizontal ultrasonic SH0guided waves for simulated corrosion defects with various geometric configurations in grounded flat steel. The simulation investigated the propagation and attenuation characteristics of the SH0 wave in grounded flat steel and the detection of various defects for linear analysis of the results. The simulation results show that the attenuation of the electromagnetic ultrasonic guided wave is small, at only 0.0016 dB/mm, and the displacement amplitude of the echo signal decreases with the increase of the SH0 wave propagation distance. Increasing the depth and length of corrosion defects increases the echo signal amplitude. At the same time, the width of corrosion defects has little effect on the echo amplitude. Finally, a flat steel defect detection experiment was conducted, and the experimental results fit with the simulation to verify the accuracy of the simulation model. This detection method introduces a new idea for the on-site detection and quantitative identification of corrosion defects in grounded flat steel, which has significant reference value and can provide a more effective and economical method for ensuring the safety and dependability of transmission tower grounding devices.

An electric-field high energy harvester from medium or high voltage power line with parallel line

Abstract In order to effectively monitor transmission lines and transmission towers, a number of different types of sensors are needed. A lot of times, these sensors along with the transmission lines and transmission towers are in inaccessible or hard-to-access areas and replacing their batteries is difficult. Yet they need consistent power supply. By harvesting energy directly from these medium and high voltage power lines, these devices can become self-sustaining while the overall system is more friendly to the environment. This paper presents a novel approach to high energy harvesting based on capacitive coupling between the power line and the harvesting line. This technique has several advantages, namely high output voltage, easy adjustment of coupling coefficient, and low cost. The validation and implantation of this harvesting system are proposed with the support of experimental results. This energy-harvesting ability of W and mA levels is achieved for the power line monitoring devices, with higher power output depending on the length and the size of the harvesting line.