Line Conductors Research Articles

The Role of AC Resistance of Bare Stranded Conductors for Developing Dynamic Line Rating Approaches

Overhead transmission line conductors are usually helically stranded. The current-carrying section is made of aluminum and/or aluminum alloys. Several factors affect their electrical resistance, such as the conductivity of the conductor material, the cross-sectional area, the lay length of the different layers of aluminum, and the presence of a steel core used to increase the mechanical strength of the conductor. The direct current (DC) and alternating current (AC) resistances per unit length of stranded conductors are different due to the effect of the eddy currents. In steel-reinforced conductors, there are other effects, such as the transformer effect due to the magnetization of the steel core, which make the AC resistance dependent on the current. Operating temperature also has an important effect on electrical resistance. Resistive losses are the main source of heating in transmission line conductors, so their temperature rise is highly dominated by such power losses, making it critical to know the value of the AC resistance per unit length when applying dynamic line rating (DLR) methods. They are of great interest especially in congested lines, as by applying DLR approaches it is possible to utilize the full line capacity of the line. This paper highlights the difficulty of accurately calculating the electrical resistance of helically stranded conductors, especially those with a magnetic core, and the importance of accurate measurements for the development of conductor models and DLR approaches.

Investigation of distribution system modification using operation voltage unification in order to decrease interruptions in dust climate

Many events in power networks which caused failure and outage of subsystems have root in design and initial selection of equipment and their specification. This concern will be important while the any kind of expanding and acclimation plan need to be executed to strengthen the existing infrastructures in order to provide better condition with regard to satisfied criteria. In Iran one of the most adverse environmental occurrences known Fine Dust, may force several distribution utilities to be changed due to new technical requirements. Medium voltage level regrading in way to decrease or unification of distribution system have been proposed in this paper to reach reduced faults and fast replacement of equipment in damaged situations. Voltage level changing and selection have been investigated in order to increase the network strengthen and reselection of equipment and redesigning critical sections of system against natural events that called fine dust with aim to attain an upgraded distribution utility. Operating of existing 33 kV and 11 kV network in 20 kV level and investigation of changing process have been done for Ahvaz medium voltage distribution system as a case study in these paper's sections. Calculations and results will be contained maximum current capacities in different line conductors, insulation and air clearances assessment, poles acceptable mechanical values, short circuit current and protection coordination for changing voltage level in distribution system.

Online sensing method for transmission line conductor ice cover based on fiber optic sensing information fusion and continuous wavelet decomposition

Online sensing method for transmission line conductor ice cover based on fiber optic sensing information fusion and continuous wavelet decomposition

Dynamic response of a transmission conductor following delayed ice shedding by reduced-scale model test

Ice shedding on conductors of transmission lines can induce severe vertical vibrations and abrupt tension changes, potentially causing structural damage and power outages. Prior experiments and numerical simulations assumed that ice sheds instantaneously from transmission lines, neglecting the practical delays in the ice shedding process, which resulted in unrealistic conductor dynamic responses. This study introduces a reduced-scale modeling system designed to simulate delayed ice shedding on conductors. The jump height and dynamic tension of an isolated-span transmission line following delayed ice shedding are analyzed, and various factors such as the two-dimensional delay duration, shedding sequence, and weight of ice accretion are examined through reduced-scale model tests. Based on the experimental data, simplified formulas are proposed to calculate the conductor's jump height and maximum tension after ice shedding by taking the time delay of the shedding process into account.

Failure type and failure level detection of insulators according to monitored leakage current

Due to the ever-increasing growth of electric energy consumption, the production of high-quality, reliable and high-reliability electricity is very important. Therefore, it is essential to have distribution and sub-transmission networks with a good reliability factor. In power distribution and sub-transmission lines, it is necessary to somehow isolate the conductors under voltage from the towers, and insulators are used for this purpose. These insulators have two main tasks. One of the main tasks of insulators is to isolate (insulate) the line conductor from the body of the tower. The insulators must be able to isolate the high voltages of the lines from the body of the tower without having a leakage current, and on the other hand, the insulators must be able to withstand the mechanical forces resulting from the weight of the conductors and the applied forces caused by wind and ice. Also, leakage current is one of the important parameters for condition monitoring of insulators in power grid lines. Failure to inspect the insulation for contamination and health conditions will lead to insulator failure and will cause faults in the electrical system. Therefore, it is very important to monitor the condition of the insulator. Based on this, in this paper, according to the data related to leakage current and also according to the introduced wear out function, a procedure for measuring the condition of insulators has been obtained. Finally, the condition of each insulator will be determined according to the defined indicators. Also, the failure level of each monitored data will be obtained using sensitivity analysis.

Sag and Tension Calculations for High-Voltage Overhead Line Conductors

Overhead lines are used to transmit electricity from where it is generated to the receiving stations. The correct design of an overhead line affects public safety, because it should ensure the required clearances between conductors and the ground and objects located in the space under the overhead line. The temperature of conductors in overhead lines depends on the load current and weather conditions, and affects the sag and tension of the conductors. Calculations of sags and tensions of overhead conductors can be performed using simplified calculation methods that do not consider insulator sets. In some situations, this approach may cause calculation errors. This article discusses algorithms for calculating overhead conductor tensions and sags in the tensioning sections of high-voltage overhead lines, accounting for and excluding insulator sets. The analysis is carried out for different lengths of tensioning sections and various thermal and mechanical states of the conductors.

Dynamics of Surge Corona Growth on Line Conductors

Dynamics of Surge Corona Growth on Line Conductors

Characterisation of the damping performance of a Stockbridge damper from laboratory tests of an overhead high-voltage transmission line conductor

Characterisation of the damping performance of a Stockbridge damper from laboratory tests of an overhead high-voltage transmission line conductor

Field Natural Experimental Study of Ice Growth Characteristics of Split Conductor and Single Conductor on Hybrid Freezing Icing

Abstract Transmission line icing seriously endangers the safe operation of transmission lines. At present, most of the research on transmission line icing is based on numerical simulation, and the growth law of transmission line ice in a natural environment has not been explored and studied. In this paper, natural ice-covering experiments are carried out in the Xuefeng Mountain Field (Natural) Ice Covering Test Base of Chongqing University, and single conductor, three-split, and four-split conductor ice-covering change rules in the mixed rime ice environment are explored. Test results found that the wind direction has a greater impact on the ice, and the windward side of the conductor ice is much larger than the leeward side. The downwind side of the ice of both single conductor and split conductor is smaller than the upwind side. The weight of ice on the split conductor line on the downwind side is about 86% of that on the upwind side. The results can provide a reference for the design of external insulation of UHV DC transmission lines.

Enhancement of transmission line parameters for the supply of energy in the Rivers state local government area of Obio Akpor

Efficient energy transmission is crucial for meeting the growing demand for electricity, particularly in urban and rural areas. In the Rivers State Local Government Area of Obio Akpor, Nigeria, ensuring reliable power supply is essential for supporting economic development and improving quality of life. However, challenges such as transmission line losses, voltage fluctuations, and inadequate infrastructure hinder the effective distribution of energy in the region. This article presents a comprehensive study on enhancing transmission line parameters to improve energy supply in Obio Akpor. Through field measurements, data analysis, and simulation studies, the performance of existing transmission lines is evaluated, and strategies for enhancing efficiency and reliability are proposed. The literature review explores previous research on transmission line optimization, emphasizing factors such as conductor material, line design, and insulation to minimize losses and maximize power transfer capability. Materials and methods encompass data collection, including impedance measurements, voltage profiles, and load characteristics, followed by computer simulations to assess proposed enhancements.

Studies on the Evolution of Fatigue Strength of Aluminium Wires for Overhead Line Conductors.

Traditional ACSR overhead wires, which consist of a high-strength steel core and several layers of aluminium wires, are currently the most popular overhead line conductor (OHL) design globally. Operating conditions, particularly operating under varying stresses from Karman vortices, lead to the fatigue cracking of wires of the outer layer, followed by wires of the inner layers. Karman vortices are formed by the detachment of a laminar wind stream flowing around the conductor, which causes vibrations in the conductor called wind or aeolian oscillations. Aluminium wires are manufactured using standard batch material drawing technology. Although the fatigue strength of such wires is not standardised, there are various criteria for evaluating this characteristic, as well as established limits on the number of cycles needed to break the first wires of the outer layer. Fatigue strength also strongly depends on the geometric structure of the wire and its operating conditions. The article analyses the influence of the mechanical condition of aluminium wires used in ACSR cables on their fatigue strength. We then present results from aluminium wire fatigue tests conducted on a specially constructed test rig. In addition, fatigue cracks were interpreted using scanning microscopy.

Degradation of superhydrophobic aluminium overhead line conductor surfaces

AbstractIt has been shown that noise emissions from HV overhead line conductors can be reduced under rain conditions by making their surfaces superhydrophobic. The working environment makes ensuring the longevity of any treatment a major challenge. The degradation of various superhydrophobic surfaces generated by applying a superhydrophobic coating and patterning microscale channels is assessed under an AC electric field (18 kV/cm) with continuous water spray. By examining the droplet distribution on the surfaces during the degradation and the surface roughness before and after degradation, the authors demonstrate that no water droplets were found on the microscale patterned surface, but droplets were formed on the coated surface after degradation. The surface roughness reduction of the coated surface and microscale patterned surface was 29.8% and 11.3%, respectively, indicating that the microscale patterned surface has better durability than the superhydrophobic coating under the AC electric stress.

Research on online monitoring method for time-varying tension in transmission lines based on operational modal response

The cumulative overload of conductor tension under severe weather conditions is an important cause of accelerated fatigue fracture of transmission lines. Traditional tension measurement methods require the replacement of ball head hanging rings, which poses safety risks. In this paper, a method for monitoring conductor tension based on acceleration data under operating conditions is proposed. Firstly, a modal order extraction based method for identifying the modal frequencies of conductor operation is proposed, and then the time-varying tension of the conductor is estimated based on the instantaneous modal frequencies. Since this method directly installs sensors on the conductor, there is a certain error in the obtained intrinsic characteristic data of the conductor. Therefore, a modal correction method is used to remove the influence of the sensors. The accuracy of modal identification, modal correction, and tension identification methods is verified through finite element models. Based on the above methods, a monitoring system for conductor tension status is designed, and the feasibility of this system is verified through experiments. Finally, the vibration data obtained from the field engineering pilot test is successfully used for conductor tension analysis. The results show that the proposed method can effectively identify time-varying tension and provide a new approach for monitoring the status of transmission line conductors.

Low insertion loss interposer approach for RF applications based on commercial LTCC tape, alkaline-free glass and printed metallization

Materials with high RF performance are in increasing demand due to the needs of modern telecommunications. Glass and low-temperature co-fired ceramics (LTCCs) are both interesting candidates for the design of complex signal transmission systems. Glass can be processed in large panels, and has suitable structure dimensions for silicon processing, but its multilayer capability is limited. LTCC is a mature technology for complex multilayer assemblies, but the structure dimensions and conductor line resolution are restricted by the need to use screen printing technology. The approach presented here combines the advantages of both technological domains: a thin glass sheet is bonded with no additional material to a LTCC multilayer ceramic and sintered to form a tight joint. Metallization of the glass is created using printable pastes and electroplating. Two fabrication routes are compared: etching of printed thick film metal layers, and semi-additive structuring. The results of RF measurements show a low attenuation per unit length for both types of metallization, indicating that our approach is a promising one for the integration of heterogeneous systems of RF transmission modules.

Analyzing the role of emissivity in stranded conductors for overhead power lines

Emissivity and absorptivity are important parameters in overhead power line conductors that depend on the conductor surface condition, so their values change as the conductors age. They have an important effect on their thermal behavior, so it is important to know their value when designing dynamic line rating (DLR) strategies. DLR methods are becoming increasingly important, especially in areas with congested power lines, as they allow the full capacity of the lines to be utilized by dynamically determining their maximum allowable currents without exceeding the safe temperature limits of the conductors, thus ensuring that they operate within safe limits. However, measuring emissivity and absorptivity is non-trivial and requires complex tests that cannot be performed in the field. Using simulations based on a realistic thermoelectric model and experimental tests performed on three types of transmission line conductors in a high-current laboratory, this paper shows the importance and effect of emissivity on conductor temperature. It also presents a method for measuring the emissivity value based on adjusting the emissivity and absorptivity values in the thermoelectric model to match the experimental values. The results presented show that aged conductors allow an increase in the maximum current carrying capacity compared to new conductors in the order of 5–14 %, depending on the conductor type considered and the operating conditions.

Modeling and Loading Effect of Wind on Long-Span Cross-Rope Suspended Overhead Line with Suspension Insulator

The long-span Cross-Rope Suspended (CRS) system is composed of a transmission line (conductor), a long-span suspension cable, and an insulator. The previously introduced long-span CRS with a Tension Insulator (CRSTI) has shown applicability in mountainous areas. However, the tension insulator divided the suspension cable into several sections, which made the construction of a long-span CRS rather difficult. This paper introduces long-span CRS with a Suspension Insulator (CRSSI), in which the suspension cable was not disconnected, and the conductor was supported by a suspension insulator connected to the suspension cable. For the purposes of assessment, the initial shape of the suspension cable with concentrated loading from the self-gravity of the suspension insulator and the conductors was studied, and practical lengths in construction could be calculated exactly. Secondly, the structural performance of CRSSI, including its dynamic properties and the loading effect of wind, was discussed by means of numerical analysis. Vibration modes of the structure were obtained by FE analysis. Finally, structural deformation under static wind loading was studied. The result of the analysis showed that the stiffness of CRSSI was lower than CRSTI. The first frequency of CRSSI was 6% smaller than CRSTI. Regarding static wind loading, additional displacement of the insulator contributed to the maximum displacement of long-span CRSSI. Apparently, the displacement of the suspension insulator increased with wind speed. Moreover, the number of spans has an insignificant influence on tension force and deformation.

Computation of corona generated ionic current environment of unipolar UHVDC transmission lines using gas bimolecular collision theory

Corona on UHVDC transmission line conductors initiates corona power loss and the inevitable ionic current flow environment at ground level. To limit this substantial flow of ionic current at ground levels, it is necessary to establish an appropriate line design configuration, including the diameter of the line conductor and the height level above the ground. It is a tedious and expensive process to establish this appropriate line design solely based on experimental findings. Hence, the computational based numerical analysis with the support of final experimental validation aids in arriving at a safe and optimal transmission line design dimension configuration. Thus, the ionic current flow environment of UHVDC transmission lines may be characterized by ionized space charge density, ionic current flow, and electrical field distribution. To estimate this ionic current flow, it is necessary to estimate the ionized space charge density in the ionization region, which incorporates the solution of the Poisson's equation. It is intricate to solve Poisson's equation with known boundary conditions: as ionization process depends on the atmospheric parameters also. Multiple computational techniques are developed to estimate the corona generated ionic current environment under the HVDC lines by waiving these atmospheric parameter effects and claims the lack of computational accuracy. In this paper, the unipolar corona equation, usually called Poisson's equation was solved by estimating the space charge ion density using the concept of gas bimolecular collision theory. The gas bimolecular collision theory inculcates the procedure to estimate the collisional reaction rate constant between the gas molecules at given atmospheric temperature and pressure parameters. Therefore, this paper developed a unique equation solution for the estimation of transition of the ionic current magnitudes at known atmospheric temperature and pressure ambient conditions. This unique equation solution prevents the multiple actual testing procedures offers to obtain safe and optimal line design dimension configurations. Multiple experimental studies are carried out up to ± 900 kV to compare the computed results in the outdoor and indoor climatic conditions at the ultra-high voltage laboratory, CPRI. Also, the computed results are compared with the results published in the literature. Based on the comparison of results, the developed computational technique exactly matches the experimental results and claims improved accuracy compared to other computational techniques.

Partial discharge pattern recognition algorithm of overhead covered conductors based on feature optimization and bidirectional LSTM‐GRU

AbstractRecognition of partial discharge (PD) patterns is essential for insulation diagnosis of covered conductors in overhead lines. Current research has not sufficiently addressed the complex background noise in real environments, and most detection methods depend primarily on feature engineering or deep learning, suggesting potential for improvement in accuracy and efficiency. This has led the authors to propose a PD pattern recognition algorithm that integrates feature selection and deep learning. This algorithm incorporates the design of a discrete wavelet denoising function specifically tailored to the characteristics of PD for data preprocessing. It employs Bayesian optimization algorithms and light gradient boosting machines for characterizing corona discharge features. Furthermore, it develops multi‐scale clustering features and phase‐resolved features for feature fusion, and constructs insightful features based on the light gradient boosting machine. Finally, a novel deep learning model is formulated, demonstrating exceptional detection performance for early faults in covered conductors. Experimental results show that this algorithm attains an Matthews correlation coefficient score of 0.814, a 13.2% improvement over the baseline algorithm's 0.719, and a speed increase of 39.18%. The final accuracy amounts to 97.85%. This algorithm demonstrates exceptional performance in detecting early insulation faults in conductors.

Reduction of Electric and Magnetic Field Emissions caused by Overhead Power Lines

Calculations and measurements of magnetic and electric fields of overhead power lines existing in Slovenia show that electromagnetic field emissions on the border of overhead power line right of way could be too high. The allowed electromagnetic field emissions defined by Slovenian government in 1996 are very strict especially for newly constructed overhead lines. For that reason some modification should be applied for newly constructed overhead lines. This paper proposed a few solution of aforementioned problem regarding arrangements of overhead power line conductor.

Analytical Estimation and Experimental Validation of the Bending Stiffness of the Transmission Line Conductors

The bending stiffness of transmission line conductors can vary significantly, ranging from maximum stiffness when behaving monolithically to minimum stiffness when wires behave loosely. This large range makes it challenging to estimate stiffness accurately at intermittent bending stages. To address this issue, a mathematical model that accounts for both frictional forces between wires in the same layer and the clenching effects of helical wires from preceding layers is proposed in this paper. The proposed model estimates cable bending stiffness as a function of axial load and curvature for multilayered strands by considering slip caused by wire behavior. To evaluate the bending stiffness, experiments were conducted on Panther and Moose Indian Power Transmission line conductors. The proposed slip model considers Coulomb frictional effects and clenching effects caused by Hertzian contact forces, filling the void in the estimation procedure. Additionally, the model considers the wire stretch effect, a parameter not previously accounted for in cable research. The predicted numerical results of the proposed model were found to vary within a maximum of 7% from the experimental tests. The proposed mathematical model thus offers a more accurate and comprehensive way of estimating the bending stiffness of transmission line conductors, addressing the existing limitations in the estimation procedure.