Transmission Tower-line System Research Articles

In-event surrogate model training for regional transmission tower-line system dynamic responses prediction in realistic hurricane wind fields

Surrogate models have shown improved accuracy in predicting infrastructure responses during dynamic loadings. However, training a surrogate model for complex loading inputs across the entire hazard region remains challenging. This study provides insight into the training of surrogate models to estimate the responses of transmission tower-line structures in a coupled high-dimensional and high-resolution wind field and presents innovative methods for addressing these challenges. Four data- and physics-based spatial-temporal decoupling sampling methods are employed and cross-compared to obtain the most representative in-event wind profiles for training the surrogate model. Long Short-Term Memory (LSTM) is utilised as the surrogate model framework to predict the dynamic responses of the structure during the 2017 Hurricane Harvey. The accuracy and robustness of two transmission tower-line structure configuration surrogate models are validated by comparing the predictions with finite element analyses by using randomly distributed temporal and geospatial wind profiles throughout the hurricane. Finally, a single LSTM surrogate model is developed, trained by applying the full reference wind speed range of Hurricane Harvey for the regional-scale structural performance evaluation of the transmission tower-line system. The results demonstrate that the proposed surrogate model training methodology is general and can be applied to regional-scale structural performance evaluations.

Fragility Analysis of a Transmission Tower-Line System Subjected to Wind and Ice Loads Considering Fatigue Damage

Disasters such as ice and wind can pose a serious threat to the normal operation of power transmission lines. Wind-induced fatigue damage can further reduce the load-carrying capacity of transmission towers, increasing their fragility to ice and wind disasters. To assess the comprehensive capability of transmission towers to resist extreme ice and wind disasters, this paper proposes a failure probability evaluation framework for transmission towers considering wind-induced fatigue damage under the coupled effect of ice and wind. Taking a certain transmission line in Hunan as an example, the failure probability caused by ice and wind disasters is calculated for different years of service. First, based on the historical meteorological data in three cities in Hunan, a joint probability model of wind speed and wind direction considering their correlation is established using the copula function. Then, based on this probability model, the wind-induced fatigue damage of transmission towers is calculated using the Miner linear damage theory and the S-N curve. Subsequently, the fragility of the tower under the coupled load of ice and wind is calculated for different years of service. Finally, by combining the structural fragility function with the joint probability distribution model of ice thickness and wind speed, the collapse probability of the transmission tower under the action of ice and wind disasters is calculated. The results indicate that the influence of wind-induced fatigue damage cannot be ignored when transmission towers encounter ice and wind disasters. With increasing service time, the ability of transmission towers to resist ice and wind disasters gradually decreases, and the failure probability also increases under extreme ice and wind conditions.

Research on ice shedding and broken conductor in tower-line system based on CR method

In cold climates, the damage to the transmission tower-line system is usually caused by ice shedding, broken conductors, and broken ground wires. To replicate the ice shedding and broken conductor scenarios more accurately and expeditiously within the transmission tower-line system, we have engineered a finite element computational program leveraging the co-rotational theory method, utilizing the C++ programming language. Additionally, we have orchestrated its visualization interface utilizing the QT and Visualization Toolkit (VTK) platforms. This program can accurately and rapidly simulate large displacement geometric nonlinear problems. An ice detachment criterion considering the resultant acceleration is proposed. Compared with previous judgment criteria, the criterion proposed in this article can adapt to the previous prediction accuracy and is more efficient in calculation. A finite element method for disconnection simulation of “node failure” was proposed, and its accuracy and computational efficiency were verified by comparison with experiments. By analyzing the coupling effect of disconnection and deicing in the tower line system, it is concluded that ground wires often have a stronger deicing effect than conductors. Although broken conductor will cause large-scale ice shedding from the span, the impact on the most dangerous point of the tower will be very small, this providing a theoretical basis for ice-covered broken conductor in the tower-line system. The simulation method proposed in this article also provides a new research idea for the simulation of ice shedding and broken conductor of tower-line systems.

Wind-Induced Response Analysis of the Transmission Tower-Line System Considering the Joint Effect

Wind load is one of the main control loads of transmission tower-line systems. Numerical simulation is the main method for studying the structural wind-induced response. The establishment of a refined transmission tower simulation model is the basis for accurately analyzing the dynamic response of a transmission tower-line system under a wind load. This paper first considered the mechanical properties of bolted joints under cyclic loading and established a transmission tower-line system model considering the joint effects. Then, the wind load was generated by the harmonic superposition method, and the wind dynamic time-history analysis of the tower-line system was conducted. The influence of the joint effect on the wind-induced response of the transmission tower-line system was studied, and the effects of turbulence intensity and wind attack angle on the bolted joint slip effect were discussed. The results showed that the joint effect significantly increased the displacement response of the transmission tower subjected to wind loads and affected the normal service performance of the tower-line system. When the turbulence intensity is 10%, the top displacement of the tower model considering the joint effect is approximately 2 times that of the ideal rigid frame model. After considering the joint effect, the additional [Formula: see text] effect caused by the increased displacement resulted in an increase in the stress of 75.6% members, and the maximum stress of the main member was located near the upper diaphragm of the tower leg. Therefore, considering the joint slip effect in angle steel transmission towers can improve the accuracy of the dynamic response analysis of transmission lines.

Shake table test and seismic fragility analysis of transmission tower-line system considering duration effect

Although extensive attention has been devoted to the influence of ground motion duration on the seismic performance of various structures, the integration of the duration effect into the seismic analysis of transmission tower-line systems (TTLSs) has been rarely studied, leading to a lack of understanding regarding the relationship between the ground motion duration and the seismic response of TTLSs. This paper aims to quantify the duration effect on the structural performance and seismic fragility of a TTLS through shake table tests and numerical simulations. To achieve this goal, a reduced-scale experimental model of a TTLS is carefully designed and fabricated, and a group of ground motions with contrasting durations is chosen using a spectral matching method. Subsequently, shake table tests are conducted to examine the duration effect on the seismic responses of the TTLS. The recorded data indicates that long-duration ground motions (LDGMs) significantly amplify the seismic responses and have the potential to degrade the structural performance. Furthermore, a validated finite element model of the TTLS is employed to compute its nonlinear responses from elastic behavior to complete plasticity utilizing incremental dynamic analysis. Probabilistic assessments are also conducted to investigate the seismic fragility and loss of the TTLS. The findings reveal higher damage probabilities and more severe losses caused by LDGMs, emphasizing the importance of considering the duration effect in the seismic performance assessment of TTLSs. This investigation contributes to a meaningful exploration for reliably assessing the seismic capacity of TTLSs while accounting for the duration effects.

Projections of severe weather and the impacts on transmission line towers in Santa Catarina, Brazil, under future scenarios of global climate change

Transmission line towers are highly exposed to weather hazards. In southern Brazil, several damages to transmission lines have been reported due to severe weather events. Climate change projections indicate that the frequency and magnitude of extreme events may increase, making planning and adaptation of the transmission system exposure even more critical. In this work, we propose a severe weather index (SWI) as a proxy for detecting severe storms that can potentially result in extreme weather events. The SWI combines thresholds of instability indices based on observed severe events around the transmission tower-line systems. These indices were calculated using the downscaling by the Eta model at 20 km resolution of three global climate model projections and at 5 km of one global climate model for the historical period and the near future. The results show that the SWI captures the severe storms observed in the region. All downscaling projections agree with the increase of extreme weather events in the near future and the expansion of vulnerable areas. The constructed index can be employed to assess the risks and to plan the power transmission system better.

A Kriging-based probabilistic framework for multi-hazard performance assessment of transmission tower-line systems under coupled wind and rain loads

A Kriging-based probabilistic framework for multi-hazard performance assessment of transmission tower-line systems under coupled wind and rain loads

Analysis of the Seismic Response of a High Voltage Transmission Tower-line System under Multi-support Excitation

Analysis of the Seismic Response of a High Voltage Transmission Tower-line System under Multi-support Excitation

Dynamic Response of Transmission Tower-Line Systems Due to Ground Vibration Caused by High-Speed Trains

With the continuous expansion of the scale of power grid and transportation infrastructure construction, the number of crossovers between transmission lines and high-speed railways continues to increase. At present, there is a lack of systematic research on the dynamic characteristics of transmission tower-line structures crossing high-speed railways under vehicle-induced ground vibration. This article focuses on the phenomenon of accidents such as line drops when crossing areas in recent years and establishes a high-speed train track foundation soil finite element model in ABAQUS that considers track irregularity. The three-dimensional vibration characteristics and attenuation law of train ground vibration are analyzed. Acceleration data for key points are also extracted. A separate finite element model of the transmission tower-line system is established in ANSYS, where acceleration is applied as an excitation to the transmission tower-line system, and the coupling effect between the tower and the line is considered to analyze its dynamic response. Subsequently, modal analysis is conducted on the tower-line system, providing the vibration modes and natural frequencies of the transmission tower-line structure. The effects of factors such as train speed, soil quality, and distance from the tower to the track on the dynamic response of the transmission tower-line system under vehicle-induced ground vibration are studied. The results show that the speed range (300 km/h–400 km/h) and track distance range (4.5 m–30 m) with the greatest impacts are obtained. The research results can provide a reference for the reasonable design of transmission tower-line systems in high-speed railway sections.

Study on wind-induced fatigue performance of large-span transmission tower-line system considering the combined distribution probability of wind direction and speed

To accurately evaluate the fatigue life of transmission line structures under wind loads, this study proposes a multivariate member fatigue damage analysis method for investigating the wind-induced fatigue performance of a large-span transmission tower-line with full consideration of the combined distribution effects of wind direction and speed in the actual wind field. With the background of in-service transmission line project, a refined finite element model of the large-span transmission tower-line system is established, and the wind load is simulated and generated based on the linear filtering method. According to the meteorological statistics of the project site in the past 50 years, the wind-induced fatigue sensitivity analysis of the tower-line system is performed through considering the combined distribution probability of wind direction and speed. The wind-induced fatigue damage of the tower-line system is calculated based on the rain-fall counting method and Miner's fatigue cumulative damage theory, and its wind-induced fatigue life is further analyzed. The analysis results show that the sensitive members of the tower-line system are mainly distributed in the 2nd, 6th, 8th and 9th segments by combining the effects of wind attack angle and wind speed. The fatigue damage of the sensitive members decreases gradually with the increase of wind attack angle (0° wind attack angle damage is the largest), and the effect of wind speed on the vertical main member is larger than that of the crossarm upper chord member. Moreover, the fatigue damage at the end of the member is significantly larger than that in the center, and even at small wind speeds, the member's end can produce a stress amplitude larger than the fatigue cut-off limit. The fatigue life of crossarm upper chord members is 72.89 years, and that of the vertical main member is 77.60 years. In particular, the vertical main member should be employed as the control member for the structural fatigue life when considering extreme wind loads.

Probabilistic framework for seismic resilience assessment of transmission tower-line systems subjected to mainshock-aftershock sequences

Immediate damage to electricity transmission systems after strong earthquakes can significantly cause widespread power outages and impede maintenance activities. Whereas previous seismic resilience assessments have investigated comprehensively the recovery capability of structures under isolated mainshocks, the effect of aftershocks has received less attention. This paper introduces a probabilistic framework for resilience assessment incorporating the effect of aftershocks and utilizes it to investigate the seismic performance of a transmission tower-line system (TTLS) under mainshock-aftershock (MSAS) sequences. Exceedance probabilities for different damage states of the TTLS are analyzed using fragility curves. Multiple decision variables (including functionality loss, recovery time, recovery function and resilience indicator) are subsequently calculated to quantify the effect of aftershocks. Meanwhile, the seismic resilience of the TTLS is further assessed by considering the uncertainties associated with those decision variables. The results reveal that aftershocks exert a significant influence on the seismic resilience of the TTLS, particularly when it experiences minor or moderate damage following the mainshocks. However, as the damage to the TTLS worsens due to larger mainshocks, the role of subsequent aftershocks becomes comparatively less influential. The proposed framework provides valuable insights for infrastructure systems before and after earthquake, effectively mitigating the adverse effects of sequential earthquakes.

Effect of Traveling Waves on Seismic Behavior of Fault-Crossing Transmission Tower-Line Systems

Ultra high voltage (UHV) transmission tower-lines systems (TTLSs) are responsible for the crucial function of transmitting and distributing electrical power over long distances, which inevitably traverse active tectonic faults when passing through seismic areas. This paper investigates the seismic behaviors of the fault-crossing UHV TTLSs, taking into account the traveling wave effects of fault-crossing ground motions. Furthermore, three scenarios (i.e. the fault located at the midspan, the side span, and the one side) according to the location of the faults relative to the TTLSs, are designated to investigate the effects of fault-crossing locations on the seismic behaviors of the fault-crossing TTLSs. The results indicate that the traveling wave effects may amplify or weaken the seismic responses and collapse of the near-fault and fault-crossing TTLSs, and the effects on the longitudinal displacement responses of the TTLS are significantly greater than those in the transverse direction, but they do not affect the distribution of the collapse weak position of the TTLSs across the fault. Besides, the effect of traveling waves on the seismic behaviors of the transmission tower further away from the fault is greater than that relatively closer to the fault. This study of the impact of the traveling wave effects and fault-crossing locations on the TTLSs serves as a valuable reference for seismic behaviors of the UHV TTLSs crossing faults.

Wind induced coupling effects of transmission tower-line system at microtopography

The coupled and uncoupled Dynamic Finite Element Models (DFEMs) of the transmission tower-line system consisting of two towers and three spans of conductors and ground wires were built at the windward and crosswind slope of a cosinoidal hill. The acceleration ratios of mean wind profiles of cosinoidal mountains were summarized from previous studies, then the mean wind profile over the windward, crosswind and leeward slopes were revised. The wind loads acting on the transmission tower-line system were calculated based on the revised profile. The wind-induced dynamic responses of the coupled and uncoupled DFEMs were detected, and the coupling effects on reaction force of hanging points, displacements and accelerations at the tower top, axial forces of main rods and wind-induced vibration coefficients were analysed. The results show that due to the lack of the TMD-like effect, the uncoupled system is more sensitive to wind load and has significant wind-induced vibration compared to the coupled system, making the three-dimensional force of the hanging point, displacements and accelerations at the tower top, axial forces of main rods increasing, but the wind-induced vibration coefficients change little. Generally, the coupling effects of the tower-line system are significant. Ignoring it will make the structural design of transmission towers conservative.

Shape Memory Alloy-Spring Pendulum for Vibration Suppression of Wind-Induced Transmission Tower-Line Systems

Wind-induced vibration suppression of transmission line structures is critical for structural reliability and serviceability. In this study, a shape memory alloy-spring pendulum (SMA-SP) is proposed for a wind-induced tower-line system to improve the reliability and serviceability of the control unit. A numerical calculation method of the transmission tower line structure coupled with the SMA-SP is established with special emphasis on the solid elements of the damper. Furthermore, the effectiveness and reliability of vibration suppression on wind-induced transmission line structures are evaluated and parametric analyses are conducted; the results reveal the influences of key parameters on the performance of SMA-SP and provide design recommendations for applications. In this study, it is demonstrated that the SMA-SP provides more stable control effects on the wind-induced vibration of transmission line structures than a conventional spring pendulum (SP), and the proposed numerical method effectively demonstrates the nonlinear mechanism of the damper. The parametric analyses show that SMA-SP exhibits low sensitivity levels to variations in the tuning frequency ratio and achieves optimal reduction effects after satisfying the internal resonance condition.

Study on mechanical properties of the cross arm-insulator system under strong wind load

High-voltage transmission tower-line systems in coastal areas are often affected by strong winds, which leads to structural damage to the towers. Detailed analysis of the damage mechanism of towers is very useful to ensure the safety and stability of the power system. This paper examines the mechanical properties of the cross-insulator structure under horizontal wind load, and then the load-carrying capacity and deformation performance were analyzed based on ABAQUS. The results show that the structure is stable under the load, and the main structure is basically in the elastic working stage with insignificant flexural and torsional effects. On the contrary, the local stress of the combined link rod connected with the insulator is large; the bending deformation characteristics of the combined link rod are obvious under the maximum horizontal load the insulator can withstand. This result can provide a reference for cross-arms structural safety design.

A data-driven physics-informed stochastic framework for hurricane-induced risk estimation of transmission tower-line systems under a changing climate

Hurricanes are one of the most devastating natural hazards which result in significant damage to civil infrastructure. The transmission tower-line system is specifically highly vulnerable to hurricane effects. Recent studies have indicated that the collapse of the transmission tower-line system during hurricane events is mainly due to the joint occurrence of wind and rain. Therefore, it is important to assess the failure probabilities of these structures under wind and rain-induced loads. With climate change, those probabilities are expected to significantly change where the brunt of the damage and economic losses would be disproportionately borne by coastal communities. This study proposes a hybrid risk-responsive, data-driven and physics-informed framework which evaluates the hurricane-induced damage to transmission lines in vulnerable regions and communities under several climate scenarios. The framework is founded upon an advanced physics informed hurricane simulation model followed by a Gaussian kernel density technique to efficiently estimate the intensity measures and quantify the associated uncertainties accurately. The generated hazard intensities are coupled with fragility surfaces expressed in terms of wind speed and rain intensity. Then, the failure probabilities are obtained for the transmission tower-line system under the joint excitation and future climate scenario. The framework is applied to several coastal cities along the US east coast. It is shown that, due to the involved system nonlinearity, the obtained failure probabilities change drastically with the future climate scenario. In addition, rainfall-induced loads which significantly impact the failure probabilities of the transmission tower-line systems are not only function of the selected sites, but also depend on the considered limit state and climate scenario. Therefore, their consideration is important for the structural design and estimation of the system performance.

Seismic responses of transmission tower-line system under multi-component ground motions

In this study, shaking table tests, theoretical research, and finite element modeling analysis were conducted on seismic responses of a transmission tower-line system under multi-component ground motions. The rocking component of ground motion was determined from the original seismic record by the wavelet analysis. The shaking table tests for scale models (single tower and tower-line system) that satisfy the similarity ratio of an actual tower-line system, were performed under multiple directions of motion. Dynamic equations under multi-component (horizontal, coupled horizontal, and tilting (CHT), and coupled vertical, horizontal, and tilting (CVHT)) ground motions were first derived in theoretical studies. The finite element model based on the actual transmission tower line system was built, and the response of the system under the identical working condition was calculated. It is found that the rotational component of the ground motion cannot be overlooked and significantly impacts the seismic response of the tower-line system, which is reflected especially as the vertical motion is coupled. The tilting ground motion, the additional second-order effect, and the foundation tilting jointly cause the increase in the response amplitude and significant asymmetric displacement effect. Since this effect of tilting ground motions, the weakening effect of the transmission line to reduce the responses for the displacement and acceleration of the tower-line system is also weakened. It is, therefore, essential to consider the adverse effects of multi-component ground motions on the designing of transmission tower systems in high-intensity areas.

Collapse failure analysis and fragility analysis of a transmission tower-line system subjected to the multidimensional ground motion of different input directions

Transmission lines, which are important for maintaining economic and social operations, are vulnerable to collapse damage due to the effect of multidimensional ground motion. In this paper, a three-dimensional finite element model of a transmission tower-line system is established. Twenty ground motion records were selected from the international ground motion database. The acceleration time history is orthogonally decomposed to obtain the acceleration time history along the X direction and Y direction of the model in different input directions. Based on the incremental dynamic analysis method, the influence of different ground motion input directions regarding the collapse failure of transmission tower-line systems is studied. Taking the section draft ratio of the tangent tower as the criterion, the influence of the seismic input direction on the collapse of the peak ground acceleration (PGA) and vulnerable area of the tangent tower is analyzed. The influence of the input direction on the collapse fragility of transmission tower-line systems under different conditions is investigated based on the fragility analysis method, and the collapse margin ratio is used to evaluate the seismic capacity of transmission tower-line systems. A comparison of the results indicates that the input direction of the ground motion has a great influence on the collapse of the PGA, and the difference in the various directions is up to 0.34 g. Additionally, the change in the input direction makes it possible for collapse to occur between the fourth and fifth sections. Last, the results also indicate that the input direction of the ground motion has a great disturbance on the collapse fragility of transmission tower-line systems. The influence of the input direction of ground motion should be considered under the condition of rare ground motion (0.32–0.46 g) and extremely rare ground motion (0.54–0.64 g) in the design of the structure. The direction along and vertical to the tower-line is not the worst input direction of the transmission tower-line system. Considering only the seismic input of these two directions will cause a significant overestimation of the seismic capacities of transmission tower-line systems.

Effect of Fault Crossing Angle and Location on Seismic Behavior of Transmission Tower-Line System

ABSTRACT Transmission lines shoulder the important task of transmitting and distributing electrical power over long distances and inevitably cross active tectonic seismic faults when traversing seismic areas. Currently, very limited information is available regarding the seismic responses of fault-crossing transmission tower-line systems. In this investigation, a typical ultra-high voltage (UHV) transmission tower-line system model was developed in ABAQUS, and corresponding finite element (FE) analyses using six sets of bidirectional fault-crossing ground motion records were subsequently performed on the computer model to evaluate the effects of the fault-crossing angle (from 15° to 165°) and fault-crossing location (the midspan and side span of the system) on the seismic behaviors of the transmission tower-line system. The incremental dynamic analysis (IDA) method was utilized to investigate the collapse mechanism and overall collapse process of the system under different fault-crossing angles and locations. The results emphasized that the fault-crossing angle and location have a significant influence on the seismic response of the UHV transmission tower-line system crossing the fault. Moreover, the optimum layout of the UHV transmission tower-line system across a strike-slip fault was investigated based on the result comparisons. This study can provide a more comprehensive understanding of the seismic behaviors and the optimum layout scheme of fault-crossing transmission tower-line systems. Additionally, the lack of analyses and design guidelines for transmission tower-line systems crossing faults in international standards renders this research a useful reference for the field.

Wind fragility assessment and sensitivity analysis for a transmission tower-line system

Wind fragility is essential to performance-based wind engineering, risk, and resilience assessment for transmission towers. However, it has not been sufficiently studied due to the key issues in performance evaluation and uncertainty treatment for transmission towers. The performance of high-rise structures can be severely weakened by geometric imperfections, but these impacts have not been well addressed for transmission towers. Besides, the current uncertainty treatment only considers the tower itself although the transmission tower is part of an interconnected tower-line system that has complex interactions with wind environment. Therefore, this paper provides a systemic solution for geometric imperfections of transmission towers, where the users can clearly observe the effect of geometric imperfections on the capacity and failure positions of transmission towers. On this basis, a wind fragility framework that incorporates the uncertainties of each line component, wind environment, and aerodynamic parameters is proposed for transmission towers. Finally, sensitivity analysis was conducted to identify the significant uncertainty parameters for tower capacity and demand by sensitivity diagram. It is found that in addition to the uncertainties of the tower itself, the uncertainties of wind profile exponent, outer diameter and aerodynamic parameter of conductors have significant effects on the fragility of transmission towers.