Power Transmission Line Tower Research Articles

A Comparative Study on Lattice Tower Angle Member Capacities as Per Indian, American, and BSEN Standards

The transmission lines and Telecommunication networks are normally supported by lattice towers. Therefore, the reliability of these essentials depends much on the reliability of the towers and their foundations. In Both telecom and power transmission line sectors, the towers are mass-produced and generally based on optimized tower weight and foundation volumes. The weight of a tower is influenced to a great extent by the selection of tower configuration, choice of bracing patterns, choice of steel grade, and profile type. The towers in general are lattice types consisting of main legs, diagonals, horizontals, cross-arm members, and peak members. The telecommunication and power transmission line tower members are generally made of steel equal-angle sections. These tower members are modeled and analyzed as pin-jointed 3-dimensional space truss models and the members are subjected to axial forces, either axial compression or axial tension in nature. Estimation of member compression capacity is the most vital parameter in design as per respective local standards and proving those estimations during full-scale model tower testing if carried out. This paper presents the differences in axial compression capacity of angle members as per Indian, American, and European standards viz., IS: 802 (Part 1/Sec 2)-2016, IS 800-2007, ASCE 10-15 and BS EN 1993-3-1:2006.

EFFECT OF DISCHARGE CURRENT MAGNITUDE ON EFFECTIVENESS OF OVERHEAD POWER LINE PROTECTION AGAINST DIRECT LIGHTNING STROKES

In this paper the efficiency of lightning shielding provided by single overhead ground wire mounted atop of a double circuit self-supported 220 kV lattice power transmission line tower with a total height of 37.115 m was examined. According to the electro-geometric concept, each phase conductor of a power transmission line has an area where the overhead ground wire does not provide full protection against a direct lightning strike. The width of this unprotected area depends on the design and dimensions of overhead power line tower, the expected magnitude of the lightning current and decreases with increasing magnitude of the discharge current. The lightning protection effectiveness of upper and middle phase conductors was studied. The values of the minimum lightning current, capable of causing an insulation flashover in case of the lightning shielding failure were calculated. The minimum values ​​of the lightning current at which complete shielding is achieved have also been determined. It was found that for upper phase conductor the minimum current at which a complete lightning shielding is achieved is 7.597 kA, and it is smaller than minimum current of 8.604 kA capable to cause an electrical flashover of the transmission line insulation. For middle phase conductor the lowest current at which a complete lightning shielding is achieved is 5.976 kA, that is much smaller than minimum current of 9.206 kA leading to an insulation flashover. The results show that the specified overhead power line is protected from dangerous lightning currents. However, computations show that downward lightning flashes having a smaller current magnitude are able to bypass the shield wire and hit the phase conductors. In this regard, due to unpredictable nature of lightning, to improve the lightning protection of power lines, other measures can be applied, including the use transmission line arresters mounted on or near towers at individual points of the power line. When thunderstorm activity increases due to global warming, strengthening of lightning protection measures is justified.

ELECTRICITY TRANSMISSION AND ENVIRONMENT: EFFECT OF WIND LOADS ON LIGHTNING SHIELDING PERFORMANCE OF OVERHEAD POWER LINES

In this paper the estimation of wind load effect on the lightning shielding performance of overhead power lines was performed. According to electro-geometrical model any phase conductor has horizontal exposure width where this conductor is not protected against lightning by the overhead ground wire. A typical double circuit 220 kV lattice power transmission line tower was considered. Obtained results demonstrate that in the presence of thundercloud in windy conditions unprotected distance of phase conductor may increase due to deflections of phase conductors. Geometric locations of the conductor attachment points on the suspension insulator string and the lower point of the conductor sagging were calculated in the range of wind pressure from 0 to 800 Pa. This allowed to determine the exposure width values of a 220 kV overhead power line upper phase conductor in the same range of wind pressure values. The results show that for a minimum lightning current of 3 kA, the unprotected distance increases by 4.323 times from 4.167 m to 18.013 m when the wind pressure increases from 0 to 800 Pa (from 0 to 36.140 m/s). For a minimum lightning current of 5 kA, the unprotected distance increases by 7.735 times from 2.825 m to 21.851 m when wind pressure and wind speed vary in the same range. Although the transmission line is reliably protected against lightning strikes with currents greater than 16 kA at wind pressure of up to 200 Pa (18.070 m/s), when the wind pressure increases from 300 Pa to 800 Pa (from 22.131 m/s to 36.140 m/s), the unprotected area increases from 4.752 m to 26.204 m. In Summary, the results show that the influence of wind load must be taken into account in the tasks of calculating lightning protection of overhead power lines. Further efforts should be focused on studying the lightning shielding performance of overhead power lines of higher voltage classes.

Optimal design of FBG flexible sensor for high-precision monitoring of three-dimensional deformation of power transmission line tower foundation

During the operation of the power transmission line tower foundation, uneven settlement and horizontal sliding were formed due to the damage of the local environment or external force. It is the most direct and effective way to realize the transformation from “passive response” to “active prevention and control” by real-time and long-term monitoring of the tower foundation and providing automatic early warning. In this paper, based on FBG (fiber Bragg grating) sensing technology, a FBG flexible sensor with temperature self-compensation characteristic was developed, which can be used for real-time monitoring of three-dimensional deformation field of tower foundation. Based on the strain information measured by the sensor, a coordinate transformation fitting algorithm was applied to reconstruct the deformation field of the tower foundation. To improve the displacement sensing precision of the flexible sensor, the influence of the length of the cemented layer and the groove radius on the strain transfer coefficient was analyzed, and the orthogonal curvature obtained by the sensing point was corrected by cubic spline interpolation. In the displacement sensing experiment, the mean absolute errors along the x-axis direction after interpolation correction were 1.84 mm (Type 1), 1.52 mm (Type 2) and 1.96 mm (Type 3), respectively; the mean absolute errors along the y-axis direction were 1.64 mm (Type 1), 2.34 mm (Type 2) and 1.21 mm (Type 3), respectively. After interpolation correction, the maximum absolute error percentages of the measuring points along the x-axis were 9.62% (Type 1), 9.01% (Type2) and 10.23% (Type 3); the maximum absolute error percentages along the y-axis were 10.44% (Type 1), 9.53% (Type2) and 9.43% (Type 3). Therefore, the designed FBG flexible sensor can be competent for the task of monitoring the three-dimensional deformation field of the tower foundation, which has important significance and application promotion value.

Simulation and Structure Optimization of Grounding Circuit Model for Power Transmission Line Tower

The lightning current dispersion process through the steel bar inside the concrete pile foundation of the transmission line tower is impeded by the high concrete resistivity. In order to improve the current dispersion performance of the pile foundation, this paper proposes a method to place flexible graphite grounding electrode along the shaft wall of the tower foundation and verified its feasibility. Both single-pile and four-pile foundations are applied to build vertical grounding models of transmission line tower with three different grounding structures, respectively, including flexible graphite grounding line, flexible graphite grounding fabric and combined graphite electrode. The effect of three grounding structures on the current dispersion and resistance reduction is studied by finite-element method. Simulation results indicate that by applying the above three grounding structures on the vertical pile foundation can significantly improve the current density distribution of the excavated pile foundation and reduce the grounding resistance. When the grounding resistance is [Formula: see text], the resistance reduction efficiencies of the above three methods can reach 48.56%, 53.86% and 54.53%, respectively. Considering the limited construction area, this paper compares the foundation that is placed combined graphite grounding electrode with square-ray grounding grid, and it can be seen that by placing vertical grounding electrode can save the land area of 295.99[Formula: see text]m2. This paper can provide reference for the design of excavation pile foundation grounding structure under limited construction area.

A two-step approach for reliability-based design optimization in power transmission line towers

A two-step approach for reliability-based design optimization in power transmission line towers

Bucket-brigade Inspired Power Line Network Protocol for Sensed Quantity Profile Acquisition with Smart Sensors Deployed as a Queue in Harsh Environment

Pressure and temperature profile are key data for safe production in oil and gas wells. In this paper, a bucket-brigade inspired sensor network protocol is proposed which can be used to extract sensed data profile from the nanoscale up to kilometer long structures. The PHY/MAC layers are discussed. This protocol is best suited for low data rate exchanges in small fixed-size packets, named buckets, transmitted as time-domain bursts among high-precision smart sensors deployed as a queue. There is only one coordinator, which is not directly accessible by most of the sensor nodes. The coordinator is responsible for collecting the measurement profile and send it to a supervisory node. There is no need for complex routing mechanism, as the network topology is determined during deployment. There are many applications which require sensors to be deployed as a long queue and sensed data could be transmitted at low data rates. Examples of such monitoring applications are: neural connected artificial skin, oil/gas/water pipeline integrity, power transmission line tower integrity, (rail)road/highway lighting and integrity, individualized monitoring in vineyard or re-foresting or plantation, underwater telecommunications cable integrity, oil/gas riser integrity, oil/gas well temperature and pressure profile, among others. For robustness and reduced electromagnetic interference, wired network is preferred. Besides in some harsh environment wireless is not feasible. To reduce wiring, communications can be carried out in the same cable used to supply electrical power.

Response of Coupled Power Transmission Tower Line Systems Subjected to Blast Loads

Response of Coupled Power Transmission Tower Line Systems Subjected to Blast Loads

Estimation of voltage waveform at top of transmission line tower struck by lightning of negative and positive polarity

The object of research is a circuit that simulates a lightning strike to a tower of 220 kV power transmission line, taking into consideration the reflection of a current wave from 10 nearest towers. Computation of the voltage arising at the top of the struck tower is necessary further to determine the lightning performance of transmission line by various methods. The lightning current has several maxima, in the case of a positive impulse polarity and, accordingly, several minima, in the case of a negative polarity, which are generally being called peaks. In addition, the lightning current impulse has a non-constant steepness in the entire area of current rise up to the first peak. The approximation of the real lightning current by simplified mathematical expressions cannot take into account all its real features. For a more detailed study of transient processes caused by thunderstorm activity, there is a need to use oscillograms of real lightning currents when modeling. The problem of determining the voltage at the top of the stricken transmission line tower was solved using circuit simulation. For an in-depth study of how the shape of the lightning current impulse affects the shape of the voltage at the top of the tower struck, digitized oscillograms of real lightning currents were used. The simulation was carried out for 7 negative lightning impulses with the first peak varying from –33.380 kA to –74.188 kA. In the case of positive lightning, 3 oscillograms were used with the first peak varying from +38.461 kA to +41.012 kA. The article shows that the shape of the front of the lightning current impulse and the amplitude of the first peak of the lightning current have a decisive effect on the maximum voltage value at the top of a power transmission line tower struck by lightning. The maximum voltage occurs precisely at the front of the current wave before the first peak of the lightning current. Therefore, the back flashover of the insulation from the tower to the phase conductor is most likely at a moment in time at the front of the current wave. By the time the maximum current is reached, the voltage at the top of the tower will be reduced by several tens of percent, compared to the maximum voltage at the tower, which occurs much earlier at the front of the current wave. The conducted research contributes to the development of methods for calculating the lightning performance of power lines and extends the scope of application of circuit simulation programs.

The Emerging Conflict of Common Ravens Roosting on Electric Power Transmission Line Towers in Montana, USA

The Emerging Conflict of Common Ravens Roosting on Electric Power Transmission Line Towers in Montana, USA

Inverse Heat Transfer Study of a Power Transmission Line Tower Foundation

Abstract In some northern regions, power transmission lines are built with metal tower footings buried in the permafrost. With a high thermal conductivity, the tower footing has a significant thermal effect on the foundation and the nearby permafrost. Heat transfer models were previously developed to predict the thermal effect with line heat source assumptions, without knowing the exact spatial distribution and temporal variation of the heat source strength. This limited the accuracy of these heat transfer models. In this work, an inverse heat transfer method (IHTM) based on dynamic matrix control (DMC) theory is developed to better estimate the heat source strength representing the tower footing. The methodology is validated with numerical simulations and experimental data. It is found that the distribution of heat source varies spatially and temporally in a more complicated way than what was assumed in previous studies. The inversed heat source is then used to reconstruct the temperature fields in a tower foundation, which provides more accurate heat transfer analysis for design and maintenance of the foundation.

Machine Learning Approach to Detect Faults in Anchor Rods of Power Transmission Lines

Detecting faults on the anchor rods of power transmission line towers is an essential procedure for guaranteeing the safety, operability, and availability of the electric power system. Such a measure aims to minimize the risk of tower collapse and the associated costs due to the lack of energy, injuries to people, and damage to the reputation of the companies involved. In this letter, we report an alternative noninvasive and nondestructive detection technique through the acquisition of electromagnetic scattering parameters. A novel machine learning (ML) approach is proposed in order to achieve the advantages of such a technique and to deal with the respective drawbacks due to the complexity of signals acquired. A strategy to artificially increase the number of relevant samples in the dataset through the simulations of computational models is performed. Different ML classification algorithms are compared in the task of detecting structural faults in anchor rods in order to define the most suitable to this application. Finally, experimental results show that the methodology proposed achieves a high detection accuracy, surpassing other known methods.

Development of Compact Overhead Power Transmission Line Tower using 8-legged Configuration

Development of Compact Overhead Power Transmission Line Tower using 8-legged Configuration

Investigating performance of micropiled raft in foundation of power transmission line towers in cohesive soil: experimental and numerical study

This paper captures the behavior of micropiled rafts in power transmission line tower foundations in cohesive soil, concentrating on their uplift performance whether due to the tower position along the line or under wind loading conditions. In this regard, first a number of micropiles were driven into the ground of a project site at the ParehSar power plant, Gilan, Iran. Compression and uplift loading tests were conducted according to relevant standards. On the basis of the field data, a three-dimensional finite element model was developed and subsequently calibrated and verified. The behavior of micropiled rafts subjected to uplift, which is a typical type of loading in foundations of 230 kV four-circuit lattice towers, was then studied by means of this model in terms of a wide-ranging parametric study. In the sensitivity analyses, the impacts of various parameters, such as micropile spacing-to-diameter (s/d) and length-to-diameter (l/d) ratios along with undrained shear strength of the soil, on the uplift capacity of an individual micropile within and out of the group were investigated. Furthermore, interaction factors were computed based on diverse values for undrained shear strength of the soil, s/d ratio, l/d ratio, and grout–soil adhesion. From design and analysis perspectives, the finite element method (FEM) outputs revealed that the efficiency coefficient of micropiled rafts during uplift can be considered equal to one. Moreover, it was found that not only does the behavior of micropiles affect the neighboring micropiles immediately adjacent to the loaded one, but it also influences those in further rows, the result of which would be considering their significance as well.

Protection Method of Biological Lightning Safety around Power Grid Based on Grounding Electrode Structure

Aimed at the actual situation of fish death in fish ponds near the power transmission line towers after the thunderstorm happened in Guangdong Province in China, this paper studied the influence of the ground current on fish in the pond. Firstly, This paper studied the current density of the fish without protection. On this basis, paper studied the horizontal pole with full-shielded, the vertical pole with half-shielded, the horizontal pole with extension three kinds of protective measures and effects. Finally an effective protection scheme was put forward according to the engineering practice. The results can provide some engineering guidance and quantitative basis for the design and modification of grounding devices when the tower is adjacent to the fish ponds in southern China.

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.

In-situ monitoring the thermal regime of foundation backfill of a power transmission line tower in permafrost regions on the Qinghai–Tibet Plateau

The stability of tower foundations in permafrost regions is related to the thermal regime of the adjacent soils. The aim of this study is to investigate the ground temperature evolution in the foundation backfill of a tower, which is constructed by open excavation on the Qinghai–Tibet Plateau. Soil temperature and water content in the backfill were monitored continuously in the first three years after the tower's construction. Results demonstrated that the winter-time construction resulted in lower initial ground temperature around tower footings, and potential natural convection in the loose backfill, which facilitated the cooling in the first winter. In the following summer, the temperature in backfill was higher than that in a nearby natural field, due to the latent heat of infiltration water in the backfill and the heating of warmer undisturbed soils. The events of water infiltration led to a heating rate of 1 to 2 orders higher than that of thermal conduction in the backfill. Whereas, after one annual freeze–thaw cycle, the dominant heat transfer changed to heat conduction in the compacted backfill. The study provides valuable insights for evaluating the constructing technique and proposing mitigative measures for power transmission lines in permafrost regions.

Soil corrosion of the AISI1020 steel buried near electrical power transmission line towers

Soil corrosion of carbon steel samples buried up to hundred days close to a high voltage power transmission line tower was examined by weight loss vs. time. A higher weight loss was observed if the samples were electrically connected to the tower than if they were not. This was attributed to the influence of alternating current (AC) signals induced in the soil by the transmission line. This field study showed for the first time the influence of the AC power line on the buried structure of the tower, while other studies so far were focused only on AC corrosion of cathodically protected coated pipelines, running parallel to the transmission line. An improved method was used to measure weight loss by descaling in Clark solution. The new method substitutes discontinuous measurements, proposed in the ASTM-G1-90 standard, by in situ measurements of the weight loss during descaling, using a computer controlled microbalance.

Applications of the FDTD Method to Lightning Electromagnetic Pulse and Surge Simulations

Electromagnetic computation methods (ECMs) have been widely used in analyzing lightning electromagnetic pulses (LEMPs) and lightning-caused surges in various systems. One of the advantages of ECMs, in comparison with circuit simulation methods, is that they allow a self-consistent full-wave solution for both the transient current distribution in a 3-D conductor system and resultant electromagnetic fields, although they are computationally expensive. Among ECMs, the finite-difference time-domain (FDTD) method for solving Maxwell's equations has been most frequently used in LEMP and surge simulations. In this paper, we review applications of the FDTD method to LEMP and surge simulations, including 1) lightning electromagnetic fields at close and far distances, 2) lightning surges on overhead power transmission line conductors and towers, 3) lightning surges on overhead distribution and telecommunication lines, 4) lightning electromagnetic environment in power substations, 5) lightning surges in wind-turbine-generator towers, 6) lightning surges in photovoltaic (PV) arrays, 7) lightning electromagnetic environment in electric vehicles (EVs), 8) lightning electromagnetic environment in airborne vehicles, 9) lightning surges and electromagnetic environment in buildings, and 10) surges on grounding electrodes.

Metallurgical Investigation of a Cracked Splice Plate Used in a Power Transmission Line Tower

Steel splice plates are used in power transmission line towers. During service, some of these plates may fail due the loading stress as well as stress generated due to inclement weather condition. One such failed splice plate, cracked in the heel region of the plate has been studied in detail to find out genesis of such failure. Metallographic study of the failed plate material near the crack and away from the crack indicated presence of white hard martensite layer near the crack. Evaluation of mechanical properties of the plate material carried out at heel and edge regions had also supported the above findings. There was enhancement of hardness, yield strength, tensile strength of the plate near heel which had indicated localized hardening of the plate in this region due to presence of martensite. A substantial deterioration of the Charpy impact toughness of the material at the heel region could also be observed particularly at subzero testing temperatures due to the same reason. The material inadequacies and operational stresses must have caused the initiation and propagation of the cracks in the heel region of the plate leading to its premature failure.