Transmission Line Tower Research Articles

On the tensile capacity of single-bolted connections between GFRP angles and gusset plates-testing and modelling

The polymer composite known as Glass Fibre Reinforced Polymer (GFRP) has several advantages over conventional materials. It has been slowly incorporated into civil infrastructures. Because of lack of knowledge about the behaviour and design criteria of structural connections, the wide-spread application of GFRP in this field has been rather limited. In this study, analytical and experimental behaviour of GFRP structural angle members with gusset plate connections for net-tension strength, with an emphasis on transmission line tower connections, were investigated. Thirty-five single-lap, single-bolted connections were tested. The widths of the gusset plate and edge distance were varied. A tensile load was applied on the joint and then failure modes and the corresponding loads were observed. The effect of the plate width and edge distance on the connection efficiency was also studied. Based on the studies, the optimum plate width and edge distance were determined as three and five times diameter of the bolt, respectively. A semi-empirical analytical stress concentration model proposed by Hart-Smith (1978), is adopted to determine the cross-correlation coefficient 'C' which is linearly correlated to the stress concentration factors of composite and elastic isotropic materials. Using regression analysis, the coefficient 'C' was obtained, and an ultimate net-tension strength design formula is proposed.

Research on Soft Grounding Material with High Conductivity in Transmission Line Tower Grounding Network

For the question that the current metal grounding device has poor corrosion resistance, construction difficulties, short life-cycle and other issues, this paper chose graphite as matrix, developed a new type of soft grounding material with high conductivity material based on modification technology of carbon nanotubes. And then the preparation method was given. Compared with traditional metal grounding device, this new soft grounding device with high conductivity have lower resistance, more stable performance, stronger corrosion resistance and electrical conductivity, non-toxic and environmentally friendly, and many other advantages. This material has high practical value.

Damage Assessment and Strengthening of Transmission Line Tower at Component Level

The damage assessment and strengthening of transmission tower is an important factor to be considered for life enhancement. The transmission towerdeteriorate due to corrosion and ageing. In this paper, analytical and experimental investigation is carried out at component level on cantilever beam made of square hollow and angle section. The damage is inflicted by reducing the stiffness of the beam. The damage is assessed based on frequency response measurements. The damaged beam is strengthened through GFRP (Glass Fibre Reinforced Polymer) wrapping using araldite bonding. The analytical investigation is carried out using ANSYS software. The enhanced strength of the beam due to GFRP wrapping is analyzed and the results of experimental and analytical investigations are compared. Keywords: Damage assessment, strengthening, steel beam, cantilever beam, frequency response Cite this Article Husain Rangwala, S. Chandravadani, R. Balagopal.Damage Assessment and Strengthening of Transmission Line Tower at Component Level. Journal of Structural Engineering and Management . 2016; 3(3): 9–15p.

Protection radius of bird-preventing installation design for 110 kV suspension insulators based on withstand tests

According to IEEE Guide for Reducing Bird-Related Outages, several types of transmission line faults could be induced by birds. The number of birds increases as human awareness of environmental protection increases. Thus, the probability of suspension insulator string flashover induced by bird streamer would also increase. Analysis of transmission line faults in Yunnan, China, shows that many transmission line faults occurred in the winter bird migration zone, and most of the towers affected are 110 kV transmission line towers. Hence, investigating the flashover process of the 110 kV transmission line suspension insulator strings induced by bird streamer and designing a well bird-preventing installation for 110 kV transmission line suspension insulator strings is necessary. In this study, a simplified, self-designed 110 kV transmission line tower is utilized to experiment on the three types of 110 kV transmission line suspension insulator string with bird simulation excrement. The analysis of withstand test results has revealed the mechanism of flashover caused by bird streamer of the three types of suspension insulator string, and the protection radius R of the three types of insulator string has been presented. The mechanism of flashover and test results have been testified by means of the distributions of electric field and potential calculated by FEM method. Thus, the bird streamer caused flashover could be classified as the shortest air gap breakdown. Hence, it is valuable for designing or selecting a well bird-preventing installation.

Optimum design of steel lattice transmission line towers using simulated annealing and PLS-TOWER

This paper presents a new optimization tool for automated design of steel lattice transmission line towers in real-world engineering practice. This tool has been developed by integrating the simulated annealing (SA) optimization algorithm into the commercial PLS-TOWER software to optimize steel lattice towers for minimum weight according to ASCE 10-97 design specification using both size and layout design variables. In this context, a novel two-phase SA algorithm is specifically developed and compared with a typical SA formulation in three weight minimization problems of real-world steel lattice towers for high voltage overhead transmission lines between 110 and 400kV. The optimized designs and the CPU time required by the two SA variants are reported for each test problem and then compared with the currently available structural configurations resulting from a conventional design process in order to quantify material saving achieved through optimization.

Airborne LIDAR point cloud tower inclination judgment

Inclined transmission line towers for the safe operation of the line caused a great threat, how to effectively, quickly and accurately perform inclined judgment tower of power supply company safety and security of supply has played a key role. In recent years, with the development of unmanned aerial vehicles, unmanned aerial vehicles equipped with a laser scanner, GPS, inertial navigation is one of the high-precision 3D Remote Sensing System in the electricity sector more and more. By airborne radar scan point cloud to visually show the whole picture of the three-dimensional spatial information of the power line corridors, such as the line facilities and equipment, terrain and trees. Currently, LIDAR point cloud research in the field has not yet formed an algorithm to determine tower inclination, the paper through the existing power line corridor on the tower base extraction, through their own tower shape characteristic analysis, a vertical stratification the method of combining convex hull algorithm for point cloud tower scarce two cases using two different methods for the tower was Inclined to judge, and the results with high reliability.

FDTD-Based Lightning Surge Simulation of an HV Air-Insulated Substation With Back-Flashover Phenomena

The operating voltages of low-voltage control circuits in power plants and substations have decreased with the installation of digital control equipment. This increases the susceptibility of control equipment to abnormal surges, which arise mainly from lightning. To protect control equipment from lightning, it is necessary to predict lightning surges invading power plants and substations and design effective lightning protection methodologies. Compared with conventional simulation techniques based on circuit theory, full-wave numerical approaches are advantageous in handling three-dimensional structures such as transmission line towers, grounding structures, nonhorizontal wires, such as incoming power lines to power plants and substations, and lightning-induced effects. In this study, to apply the finite-difference time-domain (FDTD) method to the lightning surge analysis of an air-insulated substation, we first propose techniques for simulating the nonlinear breakdown characteristics of short-air-gap arcing horns and transmission line surge arresters installed in 77 kV transmission lines for FDTD-based surge simulations, and compare the breakdown characteristics calculated using the proposed techniques with measured results for validation. Second, as an example of the application of the proposed techniques to practical surge analysis, it is confirmed that we can reproduce the measured results of lightning surges invading a 77 kV air-insulated substation in the case of a direct lightning strike to its nearby transmission line tower by taking into account lightning-induced voltages arising from the lightning current flowing through the lightning channel and transmission line tower, which are commonly ignored in conventional circuit-theory-based simulations, multiphase back-flashover phenomena, and the effect of applied AC voltages.

Experimental evaluation of the wind effects on an operating power transmission tower

Static and dynamic effects on power transmission towers can be evaluated by methodologies available in codes, which suggest the use of linear static analysis. By using numerical simulations, it is possible to observe the strong influence of the geometric nonlinear behavior of transmission cables. Dynamic effects also strongly influence this behavior, with the possibility of resonance between the cables and the structure, but up to the moment, the existent analysis procedures have not been completely validated on an experimental basis. In order to validate a complete analysis methodology, experimental procedures are proposed for a suspension tower of a 138kV transmission line in use. A tridimensional anemometer was installed on this structure in order to measure the values and directions of wind speeds. Simultaneous strain values were collected on the main elements of the tower through optical extensometers. Optical sensor technology with Fiber Bragg Gratings was used, due to the characteristic of immunity to the electromagnetic field occasioned by high electric currents. The string swing angle was evaluated through a high-resolution camera and a tridimensional accelerometer. With this instrumentation, it is possible to create a complete database that correlates wind speeds with the responses of the structural set. At the moment, 5 months of data have been collected and the instrumentation is in the final testing phase and synchronized. After this step, real-time measurements will be performed.

Индукционные потери энергии в опорах воздушных линий электропередачи

Индукционные потери энергии в опорах воздушных линий электропередачи

Computational framework for mimicking prototype failure testing of transmission line towers

Traditional analysis of transmission line tower structures gives good estimate of ultimate strength but deflection estimates are much less than actual deflections measured from tests. This is caused by additional deflections due to joint properties like bolt slip in splices and splice plate deformations. These two displacement contributing factors are difficult to include in analysis. Prototype tower testing in test beds, which provides design strength evaluation and actual deflections is expensive. This paper presents a simple analytical procedure which captures not only the ultimate load and associated deflections but also the additional deflections because of bolt slip in leg splices. The formulation incorporates a corotational updated Lagrangian procedure in finite element analysis framework. The additional deflections are integrated into a nonlinear analysis formulation used for reticulated structures which also considers member buckling and yielding. To demonstrate the applicability of the formulation, towers which were experimentally tested in test beds are studied and the results are compared with strength and deflection measurements. The formulation has been demonstrated to be a reasonable alternative to expensive proto type testing.

Monitoring of subsidence with UAVSAR on Sherman Island in California's Sacramento–San Joaquin Delta

Sherman Island, the westernmost island in the Sacramento–San Joaquin Delta in California, plays a crucial role in maintaining the water flux between saline ocean water from the San Francisco Bay to its west and the rest of the Delta to its east. Land elevation below mean sea level and continuous subsidence over the past century has made this island a high priority area for investigations of subsidence and restoration in the Delta. This study reports the results of successful application of Interferometric Synthetic Aperture Radar (InSAR) data and technique to measure subsidence in the Delta, which is a coherence-challenged non-urban area. We carried out a time-series interferometric analysis of Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) L-band (23.8 cm) data, collected from July 2009–August 2014, to assess both the spatial and temporal variation of subsidence on Sherman Island. We report both large-scale (island-wide) subsidence trends and small-scale (levee/farm scale) subsidence features in Sherman Island. Assuming the subsidence is linear during the five years of UAVSAR data acquisition, subsidence rates across the island range from 0–5 cm/yr, with an average of 1.3 ± 0.2 cm/yr. We estimate our systematic uncertainty to be 0.3 cm/yr. Overall, the central region in the island has subsided at a faster rate than the rest of the island. We find our results to be consistent with previous measurements of subsidence rates at electric transmission line towers scattered throughout the island. The results of this study provide insights into several factors influencing subsidence, including soil type, water table depth, land use, land elevation and the location and time of levee repairs. Subsidence monitoring on Sherman Island is essential for maintaining a reliable water supply for the state of California and for protecting the Delta ecosystem.

Reducing monopile rotation under lateral loading in sandy soils

ABSTRACTMany structures (including transmission-line towers, bridges, tall buildings and coastal structures) are founded on piles, which are designed to transmit both vertical and horizontal forces, and resulting moments, to the load bearing strata. The design of such foundations for large lateral repeating loads (e.g. caused by wind, wave action, earthquake) and lateral earth pressures is a challenging task. This paper presents an experimental study that investigates the use of concentric rings (CRs) of small diameter (displacement) piles (SDPs) surrounding a monopile installed in dry sand, with the intention of limiting its rotation (lateral displacement) under repeated lateral loading. The test results showed that the rotation of the monopile, investigated for a range of different repeated lateral loading schemes, was reduced by 35‒75% on account of the densification of the sand achieved during installation of the SDPs and also the lateral confinement they provided to the sand located within the CRs. Significant increases to both the cyclic stiffness and load carrying resistance of the monopile under lateral loading are documented with the inclusion of the SDPs. Further experimental as well as numerical studies are necessary to validate this novel technique and to optimise the geometrical size and network pattern of the SDPs and the CRs.

Comparison of Neural Networks and Logistic Regression in Assessing the Occurrence of Failures in Steel Structures of Transmission Lines

In this work, we evaluate the probability of falling metal structures from transmission lines. It is our objective to extract knowledge about which variables influence the mechanical behavior of the operating lines and can be used to diagnose potential falling towers. Those pieces of information can become a basis for directing the investments of reinforcement structures, avoiding the occurrence of long turn offs and high costs as a consequence of damage to towers of transmission lines. The results are obtained using the history of 181 metal structures currently in operation in the state of Paraná/Brazil. For the classification of transmission lines susceptible to failures it is proposed to identify the most likely lines considering the following parameters: operating voltage, wind and relief of the region, air masses, temperature, land type, mechanical capacity, function and foundation structure. The classic technique of classifying binary events used in this type of problem is the logistic regression (LR). The more recent technique for classification, using Artificial Neural Networks (ANN) can also be applied. The results are compared through the area under receiver operating characteristics (ROC) curves.

Modelling and simulation of the grounding system of a class of power transmission line towers involving inhomogeneous conductive media

The grounding system of a class of power transmission line towers involving inhomogeneous conductive media is modelled in order to simulate its behaviour in case that a current earth fault takes place. The simulation includes structural elements of the tower and provides an estimate of the grounding resistance of the tower, assuming that a standard grounding electrode is buried as the main part of the grounding installation. The effect of structural elements on grounding resistance is discussed and a quantitative estimate of this effect is evaluated.

Choosing configurations of transmission line tower grounding by back flashover probability value

There is a considerable number of works devoted to electrical characteristics of grounding. These characteristics are important in general. However, in application to grounding of transmission line towers they are not enough to determine what grounding construction is preferable in some particular case, because these characteristics are calculated or measured apart from the grounded object, and only limited number of current (or voltage) source waveforms is used. This paper indicates reasons in favor of the fact that to choose the optimum design of grounding, the calculation model should include the tower as it is. The probability of back flashover, which provides both qualitative and quantitative estimate of the grounding structure efficiency, can be taken as the criterion for the grounding design. The insulation flashover probability is calculated on the basis of engineering method, which evaluates breakdown strength of insulation for nonstandard waveshapes, and probability data on lightning currents. Different approaches are examined for identifying the back flashover probability, as not only amplitudes but also other parameters can be taken into account. Finite-difference time-domain method is used for calculations of transients. It is found that lightning current waveform can greatly influence calculated back flashover probability value.

Fitting algorithm of transmission tower grounding resistance in vertically layered soil models

It could be quite complicate to calculate the accurate grounding resistance of transmission line towers in an vertically layered soil model, which could bring excessive time consumption and computation load to many engineering applications. In order to calculate the resistance fast and conveniently while keeping necessary accuracy, we propose an algorithm that uses the least squares curve fitting method and hyperbolic fitting functions to fit the resistivity and grounding resistance of layered soil model. An expression of the fitting function and the fitting formula of tower grounding resistance are derived theoretically according to application demands. We applied the algorithm to calculate a practical case and the result has error less than 10%.

A procedure for the size, shape and topology optimization of transmission line tower structures

This paper presents a methodology for topology optimization of transmission line towers. In this approach, the structure is divided in main modules, which can assume different pre-established topologies (templates). A general rule for the templates creation is also presented, which is based in terms of the design practice and feasibility of prototype testing. Thus, these allow that the optimal solution has an important characteristic of direct industrial application. Furthermore, during the optimization process the size and shape of the structure are optimized simultaneously to the topology choice. For numerical examples, two structures were assessed. The first one is a transmission line tower studied in CIGRÉ (2009). Eight different load cases were considered. The second one is a single circuit, self-supported 115kV transmission line tower. The structure was subjected to a cable conductor rupture scenario and a wind load hypothesis. In both examples the constraints from the ASCE 10-97 (2000) were applied. Due to the non-convex nature of the problem and to the presence of discrete variables in the procedure, the optimization was conducted through the Firefly Algorithm (FA) and the Backtracking Search Algorithm (BSA), which are two modern heuristic algorithms. The results for the size, size and shape, and size, shape and topology optimization are presented and discussed, as well as an analysis of the performance of the algorithms. It is shown that the proposed scheme is able to reduce up to 6.4% of the structural weight, when compared to a classical size optimization procedure on original structures.

Geological Hazards in Samtskhe-Javakheti Region (Georgia)

Hundreds of settlements, agricultural lands, roads, oil and gas pipelines’ routes, towers of high voltage transmission lines, hydro-technical-meliorative objects, mountain resorts, etc. are periodically experiencing strong influence of landslide-gravitational and debris flow/mudflow processes (often with catastrophic results). Almost all landscape-geographic zones—from Black Sea coastal region, to mountainous-nival, where geo-ecological situation is severely complicated, are located in dangerous area of disaster. Negative social-economic, demographic and ecological consequences caused by debris flow/mudflows and landslide-gravitational processes, are seen in all spheres of human activity. In mountainous regions there is especially complicated situation, where in conditions of extreme activation of disaster, in many cases population displacement and transfer to other regions is needed. Because of it, in second half of 20th century, tens of villages in mountainous regions were desolated and agricultural lands were abandoned. Most alarming scenario is that such events are accompanied by loss of human lives. Only after 1995 up until now geological and geo-morphological processes in Georgia caused loss of lives of more than 139 persons. Even in conditions of routine activation of disaster, total economical damages reach tens of millions of dollars, and in case of extreme development—hundreds of millions.

Atmospheric icing status and type of southwest China networks

Transmission line disconnection, tower collapse and insulator flashover caused by icing seriously threaten power system security. Ice type and state of transmission lines, which vary a lot with terrain and climate, in typical areas such as Daqing-ridge, Yak Mountain and Erlang Mountain in Sichuan Province in South China were investigated in this paper. It is shown that mixed-phase ice with obvious layered structure, low density, strong adhesive force and windward-side growth is the main type of ice threatening the security of transmission lines and insulators. There is more ice on the ends of insulators than other areas in severe cases, where all sheds of the insulator is bridged by ice. Besides, temperature, humidity and precipitation intensity are main factors influencing the icing process. As a result, terrain and climate play a leading role in determination of icing type and severity.

About Rational Phase Design for Open Overhead Transmission Line

In this work we consider optimum configuration of split phase of open overhead line. For analysis of open transmission line efficiency, we used methods of math simulation in evaluation environment MATLAB/Simulink using library elements SimScapeSimPowerSystems. We used geometrical configurations of transmission line towers and characteristics of aluminium-steel conductors as initial data for analysis. We gave recommendations about exploitation of open transmission lines for different voltage types. We found out that the minimum value of full self-compensation length in open transmission line attained with maximum approach of split phase components, keeping in mind mechanical and electrical strength of interphase spacer blocks.