Line Conductors Research Articles

The Influence of Graphene Nanoplatelets Addition on the Electrical and Mechanical Properties of Pure Aluminum Used in High-Capacity Conductors

The main objective of this research is to assess a graphene/Al nanocomposite with a higher strength and conductivity for use in high-capacity conductors in power transmission lines. In this study, the graphene/Al nanocomposite and pure aluminum specimens were prepared using ball milling of aluminum and graphene powders, the mechanical-electromagnetic stirrer casting process, hot extrusion and finally, annealing. The microstructural, mechanical and electrical behavior of the Al 1350 nanocomposite cast reinforced with 0.5 wt% graphene and unreinforced aluminum were studied at 20 °C and 180 °C temperatures. The results revealed that, by adding graphene to pure aluminum, the tensile strength, toughness and electrical conductivity increased, but the elongation of the Al–0.5 wt% GNP composite decreased at both temperatures.

Hourly wind data for aeolian vibration analysis of overhead transmission line conductors

Fretting fatigue of conductors due to aeolian vibrations is an important phenomenon for the design and maintenance of electric transmission networks. The evaluation of exposure and susceptibility of a given span to aeolian vibrations requires information on the distribution of hourly wind speed and direction. Interpolation has been used to obtain wind data at non-instrumented locations; however, their accuracy is not adequate at locations far from stations and at locations in mountainous regions. Numerical Weather Prediction data sets provide wind information on a regular grid covering equally all regions; however, the spatial resolution is not adequate. A procedure is proposed using a mass-conserving diagnostic model (WindNinja) that incorporates a detailed map of local topography to improve predictions of wind direction. A second correction is proposed to account for local surface roughness as a function of wind direction and average canopy height from high-resolution LiDAR data. The proposed procedure is applied to nine meteorological stations and two experiment sites over southern Quebec, Canada. WindNinja was found to provide good estimates for the effects of local topography in mountainous regions. Wind speed after correction provides good agreement with hourly observations as well as with Weibull distributions fitted to the actual observations.

Technical Research on New Transmission Conductor in Medium Ice Area

In this paper, aluminum conductor steel reinforced(ACSR), high conductivity aluminum conductor steel reinforced, heat-resisting aluminum alloy conductor steel reinforced, and all aluminum alloy conductor are compared and analyzed in detail from the electrical characteristics, mechanical characteristics, and annual cost. Finally, combined with factors such as production process and construction technology, the transmission line conductor that is most suitable for a 15mm medium ice area is recommended. It provides a reference for the selection of transmission lines in future design.

Analysis on the crimping quality of overhead transmission line conductors considering equivalent cross-sectional stiffness

Approximately 58% of wire failures are caused by slippage and fracture of electrical connectors, and the crimping quality analysis of connectors is based on equivalent cross-sectional stiffness. First, a JL/GLA 400/35 steel cord aluminum strand and NY-400/35 strain clamp are selected to fabricate 26 groups of specimens with different pipe penetration depths, opposite edge distances, inner diameters of the aluminum tube, and die widths. Then, through crimping tests on the aluminum tube and conductor and the steel core and steel anchor, five main crimping failures, namely, the slip at the outlet of the clamp, the slip at the outlet of the clamp with some broken aluminum strands, fracture of the aluminum tube in the non-pressure area, wire fracture at the outlet of the clamp, and separation of steel anchors, are observed. Finally, a failure analysis method for conductor crimping is proposed based on equivalent cross-sectional stiffness. Through the analysis of grip force and crimping quality, four failure modes and simplified curves of the load–displacement curve are obtained, and the failure principle of the conductor crimping is further elaborated. The results show that the stress release caused by the steel core and steel anchor of the crimping wire and the crimping aluminum tube and wire is the main reason for the slippage and fracture of the transmission line conductors and that it is also the key to improve the installation quality of the transmission line.

Electric Fields in the Vicinity of High-Voltage Power Lines, Optimisation of Power Line Design

This paper presents calculations in the distribution of the electrical fields generated by the potential of phase conductors in overhead high-voltage power lines. The calculations relate to the area between the line paths and the terrain, with particular focus on the area near the ground, which is important in terms of any humans present there, temporarily or permanently. Field intensity distribution is determined for different arrangements of phase conductors and line paths, and for different tower designs. The optimisation criterion is the width of the area excluded from residential development, defined as double the distance from the axis of the line where the electrical field strength exceeds the regulatory permitted 1 kV/m value.

NORMAL VIBRATIONS OF SAGGING CONDUCTORS OF OVERHEAD POWER LINES

The phenomenon of self-excitation of thermomechanical vibrations of current-carrying conductors, experimentally discovered by academician A.F. Ioffe, is of practical interest as a possible explanation of the phenomenon of galloping conductors of overhead power transmission lines (OHL) – low-frequency vibrations with frequencies of ~ 1 Hz and with amplitudes of the order of the static conductor sagging. To build the theoretical foundations of this phenomenon, as a special class of self-oscillating systems, it is necessary, first of all, a model of conductor vibrations in the OHL span. With regard to the most studied type of conductor vibrations, high-frequency aeolian vibration, excited by sign-alternating aerodynamic forces from the Karman vortex street, the classical model of a straight string is reasonably applied. However, to study low-frequency vibrations of the galloping type, it is necessary to take into account the effect of sagging of the conductor, the associated elastic tension and, in some cases, the nonlinear nature of the vibrations. The article presents two models for calculating the natural vibrations of sagging conductors (cables) within the framework of the technical theory of flexible threads, assuming the constancy of the tension force along the length. The first model describes linear oscillations of an elastic conductor in the sagging plane. For a system of equations with respect to the displacement components given in natural coordinates, an exact solution of the Sturm-Liouville problem with estimates of the frequency ranges arising is obtained. The second model describes nonlinear vibrations of an elastic conductor in the sagging plane and pendulum vibrations accompanied by an exit from it. The solution of the problem is based on the principle of possible displacements using the Ritz method. The structure of the frequency spectrum and the natural forms of transverse vibrations are studied. The developed models are intended for further investigation of thermomechanical vibrations of conductor and flexible cable systems.

On-Line Core Losses Determination in ACSR Conductors for DLR Applications.

Dynamic line rating (DLR) is a method that focuses on dynamically determining the maximum allowable current of power lines, while ensuring they operate within safe limits. DLR needs to monitor the temperature and current of the line in real-time, as well as the weather variables in the surroundings of the power line. DLR approaches also require determining the AC resistance of the power line conductors, which is a key parameter that enables it to determine Joule and core losses. This paper presents an approach for an on-line alternating current (AC) resistance estimation of aluminum conductor steel-reinforced (ACSR) conductors to determine the DLR capability of such conductors from real-time conductor and meteorological parameter measurements. For this purpose, conductors with one, two and three layers of aluminum strands are analyzed in detail. Based on the experimental results presented in this paper, two possible approaches are proposed.

A New Method to Distinguish between Nearby and Direct Lightning Strikes for Long Operational Medium Voltage Lines

Lightning strikes near Medium Voltage (MV) electricity distribution lines cause voltage transients to be induced onto the conductors of the power lines. The resultant Lightning Induced Overvoltage (LIOV) on the phase conductors may be estimated using computer models or measurements. Models and measurements are mostly limited to short floating lines to simplify calculations and to ensure accurate results that can be easily compared between different models. Existing measurement methods cannot be used to distinguish between nearby lightning and direct lightning strikes to an operational MV network by using only one instrument on a line that is more than 100 km long. The instrument needs to be less than a hundred meters from where the LIOV amplitude on the line is the highest. The new method described in this paper allows one to distinguish between nearby and direct lightning strikes to the line; by comparing the polarity of the current transient recorded at the substation to the lightning return-stroke polarity obtained from a lightning detection network. The new method also allows one to determine whether the LIOV of a particular lightning transient exceeded the Basic Insulation Level (BIL) of the line, by observing the power frequency fault current. The new method was applied to an operational 714 km network operating at 22 kV, and the results were compared with predictions in IEEE Std 1410-2010. Significantly fewer line faults due to nearby lightning were observed than predicted; the reason for this is explained.

How statistical modeling and machine learning could help in the calibration of numerical simulation and fluid mechanics models? Application to the calibration of models reproducing the vibratory behavior of an overhead line conductor

The world of fluid mechanics is increasingly generating a large amount of data, thanks to the use of numerical simulation techniques. This offers interesting opportunities for incorporating machine learning methods to solve data-related problems such as model calibration. One of the applications that machine learning can offer to the world of Engineering and Fluid Mechanics in particular is the calibration of models making it possible to approximate a phenomenon. Indeed, the computational cost generated by some models of fluid mechanics pushes scientists to use other models close to the original models but less computationally intensive in order to facilitate their handling. Among the different approaches used: machine learning coupled with some optimization methods and algorithms in order to reduce the computation cost induced. In this paper, we propose a framework which is a new flexible, optimized and improved method, to calibrate a physical model, called the wake oscillator (WO), which simulates the vibratory behaviors of overhead line conductors. an approximation of a heavy and complex model called the strip theory (ST) model. OPTI-ENS is composed of an ensemble machine learning algorithm (ENS) and an optimization algorithm of the WO model so that the WO model can generate the adequate training data as input to the ENS model. ENS model will therefore take as input the data from the WO model and output the data from the ST model. As a benchmark, a series of Machine learning models have been implemented and tested. The OPTI-ENS algorithm was retained with a best Coefficient of determination (R2 Score) of almost 0.7 and a Root mean square error (RMSE) of 7.57e−09. In addition, this model is approximately 170 times faster (in terms of calculation time) than an ENS model without optimization of the generation of training data by the WO model. This type of approach therefore makes it possible to calibrate the WO model so that simulations of the behavior of overhead line conductors are carried out only with the WO model.

Influence degree of skin-effect for overhead line conductors

This paper analyzes the skin-effect influence on ACSR conductors for overhead lines. The analysis is based on numerical models: one cylinder, and two coaxial cylinders, and cylinders layers. The authors compare all models with each other, as well as with the well-known analytical solution, and direct current mode. All numerical models were verified by comparison with the analytical solution. The results show the one cylinder model get incorrect results for ACSR conductors. Moreover, the maximum error about 40% is given by conductors with a medium cross-sectional area, such as the ”AC 240/39” conductor by GOST 839-2019. The two coaxial cylinders model gives better results but about 10% less than the cylinders layers model, since it does not consider the electric field penetration between wires of a conductor. As a result, the authors conclude that the skin effect has a great influence for all ACSR conductors.

ЗАХИЩЕНІ ІЗОЛЯЦІЄЮ ПРОВОДИ ДЛЯ ПОВІТРЯНИХ ЛІНІЙ ЕЛЕКТРОПЕРЕДАЧІ НА СЕРЕДНЮ НАПРУГУ: ПЕРЕВАГИ, КОМПЬЮТЕРНІ РОЗРАХУНКИ

The paper presents the advantages of protected insulated wires for medium-voltage (up to 35 kV) overhead power lines compared to the lines with traditional non-insulated wires. The mathematical model is developed and the computer calculations are realized for a 20 kV protected insulated wire with a steel-aluminum core. For such design, the distributions of the magnetic field and current density in three wires of overhead power line are analyzed, their resistance is determined taking into account the nonlinear properties of the steel core within the frequency range of 50–10000 Hz. This makes it possible to compute the electrical losses in the conductors of the power lines under the transient conditions and at high harmonics in the power network. References 8, figures 4.

Stability Bounds for Micron Scale Ag Conductor Lines Produced by Electrohydrodynamic Inkjet Printing.

Continuous conducting lines of width 5–20 μm have been printed with a Ag nanoparticle ink using drop-on-demand (DOD) electrohydrodynamic (EHD) inkjet printing on Si and PDMS substrates, with advancing contact angles of 11° and 35°, respectively, and a zero receding contact angle. It is only possible to achieve stable parallel sided lines within a limited range of drop spacings, and this limiting range for stable line printing decreases as the contact angle of the ink on the substrate increases. The upper bound drop spacing for stable line formation is determined by a minimum drop overlap required to prevent contact line retraction, and the lower bound is governed by competing flows for drop spreading onto an unwetted substrate and a return flow driven by a Laplace pressure difference between the newly deposited drops and the fluid some distance from the growing tip. The upper and lower bounds are shown to be consistent with those predicted using existing models for the stability of inkjet printed lines produced using piezoelectric droplet generators. A comparison with literature data for EHD printed lines finds that these limiting bounds apply with printed line widths as small as 200 nm using subfemtoliter drop volumes. When a fine grid pattern is printed, local differences in Laplace pressure lead to the line width retracting to the minimum stable width and excess ink being transported to the nodes of the grid. After printing and sintering, the printed tracks have a conductivity of about 15%–20% of bulk Ag on the Si substrate, which correlates with a porosity of about 60%.

Discussion on the Key Points of 220kV High Voltage Transmission Line Conductor Erection Construction Technology

Discussion on the Key Points of 220kV High Voltage Transmission Line Conductor Erection Construction Technology

Genetic algorithm optimization to minimize fields, maximize power, and inhibit corona of high voltage transmission lines by arranging the conductors

AbstractIn this paper, a comprehensive study is presented whereby genetic algorithm optimization (GAO) is used to find the best arrangement of three‐phase high‐voltage transmission line (TL) conductors, that minimizes emitted electric and magnetic fields (EMFs), maximizes power capacity, and avoids corona. Moreover, a financial cost study is conducted in order to show the feasibility of implementing such rearrangement, where construction costs are compared with the impact on a populated area in close proximity to the line. To facilitate applying the procedure of this paper, a detailed description of each step is provided. Both single circuit as well as double circuit transmission lines are considered, and bundled conductors are analyzed. To demonstrate the validity and usefulness of the mathematical formulation and MATLAB computer codes, computed results are compared with measured data where good agreement is observed. To show that using GAO for solving high voltage line problems is an alternative to other robust optimization techniques such as particle swarm optimization (PSO), GAO solutions are compared with PSO solutions. The GAO results are also compared with the unoptimized results, where significant improvements can be seen. Since according to this algorithm, line conductors move freely throughout the solution space in an attempt to find the best solution, it is important to restrict this movement in order to adhere to the separation limits of the transmission line international standards IEC‐71.

Optical wireless communication under the effect of low electric field

Abstract In this paper, the performance of free space optics (FSO) technology is investigated under the effect of external electric fields perturbations; standard parameters of the proposed system adopted by performing experimental setup measurements on the laser propagation axis and computer simulation using the “OptiSystem” program. The experimental results show linear relation between the electric field and the fluctuation of the output power As a result of the interference between the transmitted signal and the noise created by an electric field. The simulation results illustrate that when the transmitter divergence angle increased the Q-factor decreased, but not high enough to cause a complete blocking to the transmitted signal. The significance of these results, they help to understand the effect of electric discharges and Corona phenomenon of the electric field produced by the transmission line conductors nearby the optical communication systems where, (1 mrad) is the most effective divergence angle that reduces these effects.

Application of Radar-Absorbing Materials for Attenuating High-Frequency Interference in the Electrical Circuits of Aircraft Electrical Systems

Conducted high-frequency electromagnetic interference is induced in the electrical circuits of aircraft electrical systems under the effect of external man-induced electromagnetic fields penetrating into the aircraft structure through radio-transparent apertures. To attenuate the impact of the conducted high-frequency electromagnetic interference induced in the two-wire lines of electrical bundles and other electrical circuits of electrical systems on sensitive semiconductor elements and integral microchips of on-board instruments and devices, low-pass filers on the basis of lumped components are used. At high frequencies, resonance phenomena may occur in the filter electrical circuits, which degrade the filter capabilities to attenuate conducted interference. Conducted high-frequency interference can be attenuated, and their propagation paths in the two-wire lines of electrical bundles and in the electrical circuits of on-board instruments and electrical system devices can be eliminated by applying radar-absorbing materials (RAM). Conducted electromagnetic interference in two-wire lines at a frequency above 1000 MHz generates high-frequency electromagnetic fields. With RAM placed in close proximity to the conductors of two-wire lines, it is possible to attenuate conducted high-frequency interference due to absorption of the interference electromagnetic field energy. The results of experimental studies are presented, the data of which make it possible to evaluate the extent to which the conducted high-frequency interference is attenuated in the frequency band 0.1–3000 MHz by applying radar-absorbing materials.

Electromagnetic Fields Due to an Electron Avalanche

In electric power and electronic systems, localized breakdown of air in the form of corona, partial discharge (PD), and electrostatic discharge (ESD) occurs frequently. These processes are known to be sources of electromagnetic fields. Corona on overhead line conductors produces electromagnetic noise over a wide frequency range leading to electromagnetic interference. The magnetic field due to PD can be employed to detect and possibly locate PD inside the apparatus. The fields due to ESD assume importance in designing suitable protection systems. Therefore, there is a need to relate the electromagnetic field produced by the discharge phenomenon to the physical ionization process, which constitutes them. The basic mechanism behind naturally initiated electrical discharges is the electron avalanche and an expression for its total electric field has been derived and validated in the literature. The next step in this direction is to obtain the magnetic field produced by it. An expression for the complete magnetic field, i.e., both near- and far-field components, is derived starting from Lienard–Wiechert potentials. The derived expression is validated with the numerical solution of Maxwell's equation. A simplified procedure to extend avalanche results for practical discharges is demonstrated. Close agreement is obtained between the estimated results and measured results reported in the literature.

Experimental study on dynamic response characteristics of isolated‐span transmission lines after ice‐shedding

The dynamic response characteristics, including maximum jump height and unbalanced tension, of isolated-span transmission lines after ice-shedding are investigated by means of experiments. A reduced-scale modelling method for ice-shedding from conductor lines is presented and verified with numerical simulations and full-scale test results in the literature. A parameter study on dynamic responses of isolated-span conductors under three ice-shedding scenarios, including whole span ice-shedding, partial ice-shedding and unzipping ice-shedding, is carried out by means of reduced-scale modelling tests. The effects of these parameters on the maximum jump height at typical positions and unbalanced tension in the tension tower are obtained. It is observed that the partial ice-shedding scenario may be the worst situation for electrical insulation clearance rather than the whole span ice-shedding scenario. Moreover, the position of maximum jump height along the span of isolated-span transmission lines after ice-shedding could be at around 2/5 of span length, which is different from the conventional opinion that the position is at the midpoint. The results may provide a foundation for the defining of the insulation clearance for an isolated-span transmission line and the structure design of tension tower arms in an iced zone.

Optimization of the Creation of a Training Set for the Calibration of a Model Reproducing the Vibration Behavior of an Overhead Line Conductor

One of the applications that machine learning can offer to the world of Engineering and Fluid Mechanics in particular is the calibration of models making it possible to approximate the representation of a particular phenomenon. Indeed, the computational cost generated by some fluid mechanics models pushes scientists to use other models close to the original models but less computationally intensive in order to facilitate their handling. Among the different approaches used: machine learning coupled with some optimization methods and algorithms in order to reduce the computation cost induced. This paper proposes a new framework called OPTI-ENS: a new flexible, optimized and improved method, to calibrate a physical model, called the wake oscillator (WO), which simulates the vibratory behaviors of overhead line conductors. An approximation of a heavy and complex model called the strip theory (ST) model. OPTI-ENS is composed of an ensemble machine learning algorithm (ENS) and an optimization algorithm of the WO model so that the WO model can generate the adequate training data as input to the ENS model. ENS model will therefore take as input the data from the WO model and output the data from the ST model. As a benchmark, a series of Machine learning models have been implemented and tested. The OPTI-ENS algorithm was retained with a best Coefficient of determination (R2 Score) of almost 0.7 and a Root mean square error (RMSE) of 7.57e-09. In addition, this model is approximately 170 times faster (in terms of calculation time) than an ENS model without optimization of the generation of training data by the WO model. This type of approach therefore makes it possible to calibrate the WO model so that simulations of the behavior of overhead line conductors are carried out only with the WO model.

Improved Electrogeometric Model of UHV Transmission Line Based on Long Gap Discharge and Its Application

Based on long air gap discharge test data and lightning return stroke observation data, an improved electrogeometric model (EGM) considering terrain conditions is established and verified to analyze the lightning shielding performance of UHV transmission lines. The striking distance formula is modified as rs = 0.13 (I2 + 40I)0.814. In this paper, the lightning shielding failure rate of three-phase conductors of EHV and UHV transmission lines calculated by the improved EGM model is consistent with the lightning observation data of actual transmission lines in Japan and the scaled lightning discharge simulation experimental results of UHV transmission lines in plains and mountainous areas of China, which verifies the applicability of the improved EGM model to evaluate the lightning shielding performance of large-scale UHV transmission lines. The improved EGM model is applied to evaluate the influence of tower type and slope steepness on the shielding failure tripping rate of UHV transmission lines. The shielding failure tripping rate of the SZ322 tower is higher than that of the SZT1 tower, and the shielding failure tripping rate of UHV transmission lines is greatly affected by slope gradient and increases with the increase of slope gradient.