kV Overhead Line Research Articles

Methodology for selecting optimal wire grade and cross-section based on an integrated technical and economic criterion

The aim was to develop a methodology for selecting an optimal wire grade and cross-section for overhead power lines with a voltage of above 1 kV under intensive development of power grid systems. This aim was solved using the authors’ previously developed methods: selection of an optimal wire grade based on hierarchy analysis and selection of an optimal wire cross-section by optimizing the specific discounted costs during the entire period of construction and operation of overhead power lines. In the present study, these methods are integrated into a single methodology. It is proposed to implement wire inspections prior to the stage of technical and economic calculations, since the necessary data has already been taken into account during the selection of a wire grade and its cross-section. The proposed methodology was tested on a typical example of reconstruction of the Zapadnaya– Davydovka 110 kV overhead line, which creates limitations in the power supply of Primorsky Krai due to insufficient wire capacity and its operation beyond the normative period. SENILEK AT3/C 150/24 wire was selected as a solution for the example under consideration. The application of this wire grade allows not only the overhead line capacity to be increased by 151% without replacing the existing supports, but also active and reactive power losses in the electric network to be reduced by 18.9 and 2.5%, respectively. The proposed methodology enables selection of an optimal grade and cross-section of any wire design, taking the dynamically changing operational conditions of power grid systems into account. The solutions found by the proposed methodology may contribute to a more efficient operation of power lines due to increasing their transmission capacity, reducing the number of used supports, replacing the line wire without replacing supports, decreasing ice formation on wires, and reducing power losses.

INCREASING THE ACCURACY OF THE POWER LINES MODELING BASED ON PMU

The article discusses the modeling of power lines based on PMU data to assess the state of overhead lines. Current approaches to solving the problem are analyzed. The advantages and disadvantages of these approaches are presented. It has been established that when modeling power lines are traditionally represented in the form of a - circuits scheme, which leads to methodological modeling errors. To reduce the methodological error of modeling, overhead lines (OHLs) can be presented in the form of equations with distributed parameters, which allows for maximum accuracy. However, distributed line equations contain hyperbolic functions and reduce performance in real-time simulations. Based on this, it is noted that the selection of an adequate mathematical model of overhead lines with the appropriate accuracy of synchronized vector measurements in real time when assessing the state of power lines is an important stage of modeling. The article discusses overhead line models using equations with distributed parameters, a -circuits, an equivalent - circuits and chain -circuits depending on the number of links. The results of calculating the mode based on the modeling accuracy using the example of a 500 kV overhead line are presented, as well as the results of comparing various equivalent circuits. It is shown that when modeling overhead line modes based on the results of PMU measurements, representing power lines as chain circuits with links 50 km or less in length is appropriate, since it makes it possible to obtain a model accuracy that is adequate to the PMU measurements. Methodological errors in modeling ultra-high voltage transmission lines using the equations of long lines have been studied. The obtained results can be used for monitoring, analysis and operational management of the electric power system

Precise Lightning Strike Detection in Overhead Lines Using KL-VMD and PE-SGMD Innovations

When overhead lines are impacted by lightning, the traveling wave of the fault contains a wealth of fault information. The accurate extraction of feature quantities from transient components and their classification are fundamental to the identification of lightning faults. The extraction process may involve modal aliasing, optimal wavelet base issues, and inconsistencies between the lightning strike distance and the fault point. These factors have the potential to impact the effectiveness of recognition. This paper presents a method for identifying lightning strike faults by utilizing Kullback–Leibler (KL) divergence enhanced Variational Mode Decomposition (VMD) and Symmetric Geometry Mode Decomposition (SGMD) improved with Permutation Entropy (PE) to address the aforementioned issues. A model of a 220 kV overhead line is constructed using real faults to replicate scenarios of winding strike, counterstrike, and short circuit. The three-phase voltage is chosen and then subjected to Karenbaren decoupling in order to transform it into zero mode, line mode 1, and line mode 2. The zero-mode voltage is decomposed using KL-VMD and PE-SGMD methods, and the lightning identification criteria are developed based on various transient energy ratios. The research findings demonstrate that the criteria effectively differentiate between winding strike, counterstrike, and short-circuit faults, thus confirming the accuracy and efficacy of the lightning fault identification criteria utilizing KL-VMD and PE-SGMD.

A Computational Tool Focusing the Optimization of 34.5 and 138 kV Overhead Lines Transmissible Power

This paper presents a computational strategy proposal for optimise the physical arrangements of electrical power system overhead lines to increase the power transmission. The technique employs the Genetic Algorithms Theory to find the best geometric arrangement by weighting the optimal phase and sub-conductors spacing as well as the line heights. The target to be achieved is the maximum power at the receiver end. In order to emphasize the approach and the developed computational tool, the methodology is applied to typical 34.5 and 138 kV overhead lines.

The use of S460 steel grade in the construction of OHL transmission towers

AbstractThe article describes structural solutions and specialised testing of innovative steel lattice towers intended for 400 kV overhead line (OHL). A unique aspect of the preformed research is the use of S460 steel grade in the structure of such transmission towers. This new series of towers was developed in reference to current EN 50341‐2‐22:2016 standard that introduces higher safety standards for OHL towers. A full‐scale prototype was developed and analysed, where the verification of the standard load‐bearing capacity was done and proceeded by the destructive test in order to determine the ultimate capacity of the new tower typology. The article presents the obtained results, the justification for the use of S460 steel grade and a comparative analysis with the classical engineering procedures. A good agreement between a theoretical model and the test results is demonstrated.

АНАЛИЗ КОНФИГУРАЦИИ СЕЛЬСКИХ ЭЛЕКТРИЧЕСКИХ СЕТЕЙ 10 КВ

Currently, the works of domestic and foreign scientists explore options for improving medium-voltage electrical grids by introducing distributed automation tools. However, statistical data on the configuration of existing rural power grids of 10 kilovolts are not sufficiently presented in the literature. (Research Purpose) The research purpose is analyzing the configuration of rural electrical grids of 10 kilovolts, taking into account the transformer substations connected to them and the types of wires used. (Materials and methods) The analysis of 165 supporting schemes of 10 kilovolt overhead power transmission lines of one of the electric grid companies was carried out. (Results and discussion) It is found out that the arithmetic mean of the length of the overhead line of 10 kilovolts to the most remote point of the grid is 9.2 kilometers, and the total length is 13.2 kilometers. It is found that that the specific power per kilometer of the rural grid of 10 kilovolts is 82 kilovolt amperes per kilometer. At the same time, an average of 5 taps are from one 10-kilovolt line, and the average length of the them is 0.68 kilometers. It was also revealed that 72 percent of the total length of the analyzed power transmission lines of 10 kilovolts does not meet the requirements for mechanical strength under icy and wind loads. (Conclusions) The analysis reflects the current configuration of rural 10 kV power grids in the Orel region, while 10 kV overhead lines in other regions may have their own characteristics.

Monitoring of Single-Post Free-Standing Supports of Overhead Power Lines under the Action of Wind Loads

Experimental studies of the dynamic behavior of metal supports of an overhead line (OL) under the action of wind loads are presented. The methodology and scheme of the experiment execution in two stages on the anchor-angular and intermediate supports of the 220 kV overhead line “Zmiev TPP – Zalyutino” have been developed. At the first stage, the excitation of vibrations of the support structures was achieved using wind action, at the second stage, free vibrations of the “support – wires” system were recorded, which were created using manual resonance. Graphs of stress changes in structural elements of tower lattice supports in the wind along and across the overhead line are presented. The main natural frequencies of vibrations of metal supports have been experimentally determined, which are displayed on the free vibration damping graphs. Analysis of the obtained spectra of longitudinal pulsations of wind speed made it possible to conclude that the wind flow is stationary. The necessity of frequency detuning of the overhead line support structure from the natural frequency of 2.2 Hz has been established, since an external effect with this frequency is possible when the live wire breaks in one of the phases. It is necessary to improve not only the principles of monitoring and observing the behavior of structures in the wind flow, but also to develop simple methods to take into account the dynamic component under the action of natural-climatic and emergency loads, which by their nature are dynamic phenomena.

Selection of an optimal cable brand for high-voltage overhead power lines based on criterion analysis

This paper is aimed at developing a versatile approach to selecting an optimal cable brand for overhead transmission lines for use in design practice, adapted to conventional and new-generation cable types. To implement multi-criterion evaluation of external factors and limitations when selecting a cable type, the methods of systems, hierarchy and comparative analysis were used. A method for selecting an optimal cable brand based on hierarchy analysis was developed along with an algorithm for its implementation when designing new or modernizing existing overheadlines. The developed approach is demonstrated on the example of construction and modernization of 220 kV overhead lines with the conventional AC cable and such new-generation domestic brands, as АСВТ, АСВП, АСк2у and АСТ. In the considered examples, the technical feasibility of the construction of a new overhead line was limited by the value of the sag. For the modernization project, the specific weight of the cable was of greater importance. The selection criteria included the span length, cable cost and admissible continuous current. The АСВП and АСТ cable brands showed the greatest compliance with the selection criteria (27.5% and 55.9%, respectively). Therefore, at minimum capital investments, the АСВП brand ensures the optimum span length in the construction of a new overhead line, whereas the ACT brand ensures the maximum capacity in the modernization of an existing line. The conducted verification calculations confirmed the feasibility and versatility of the proposed method for selecting a cable brand.

Estimating the shielding failure flashover rate of single-circuit overhead lines with horizontal phase configuration via stochastic lightning attachment simulations

A methodology is proposed for estimating the shielding failure flashover rate (SFFOR) of single-circuit overhead lines with horizontal phase configuration. An application to a 66 kV overhead line is presented. A stochastic lightning attachment model is employed, based on the concept of fractal structures, to compute the probability of shielding failure to the line. Results of stochastic modeling are combined with those of an ATP-EMTP model for estimating the critical lightning currents causing flashover of the line insulation. Shielding failure results of the proposed methodology are compared and discussed with results obtained employing the methodology of the IEEE Std 1243. Innovation of this work lies in estimating the SFFOR of overhead lines by considering the stochastic nature of lightning attachment, physical criteria associated with leader discharges’ inception and propagation, as well as electromagnetic transient simulations to predict lightning-related flashover to overhead lines accurately.

An investigation of electromagnetic transient characteristics on a practical 500 kV submarine cable system

This paper performs an investigation on electromagnetic transients for a practical 500 kV cable system. The system consists of 500 kV overhead lines, submarine and underground cables. In order to study the insulation coordination of the cable system, the transient simulations are performed using EMTP. The modal propagation constants of submarine cable are also investigated. Moreover, the cable series and shunt parameters are calculated using the newly developed Line/Cable Data Module in EMTP. The voltage and current characteristics of the cable system in steady-state, and for switching, fault and lightning transients, are studied. The transient overvoltage levels are also compared with requirements of insulation coordination in local standards. The work shown in this paper could provide a reference for the insulation design of 500 kV cable system.

Development of a series of miniaturization device for insulation wrapping of distribution lines

With the continuous expansion of the scale of power grid in China, the traditional line inspection method has been difficult to meet the requirements of the future power system, the research and application of line inspection robot has become inevitable.Line inspection robot instead of manual line inspection, not only can avoid unnecessary dangers, but also can complete insulation repair work, inspection inspection efficiency is high [1-2]. This project by 10 kv overhead insulated package unit as the research object, according to the insulation repair the actual situation of the construction site, developed a device used for 10 kv overhead line insulation package, the robot by the ground staff through tablet computer remote control operation, to walk to the on-line control insulation package device to fix position, to repair the cable package on the wire. The whole operation process does not need power outage, so that the robot can replace the manual work to complete the insulation repair of the line [3-4].

A Cascade BP Neural Network Tuned PID Controller for a High-Voltage Cable-Stripping Robot

A 10 kV distribution network is a crucial piece of infrastructure to guarantee enterprises' and households' access to electricity. Stripping cables is one of many power grid maintenance procedures that are now quickly expanding. However, typical cable-stripping procedures are manual and harmful to workers. Although numerous automated solutions for grid maintenance have been created, none of them focus on cable stripping, and most of them have large dimensions to guarantee multi-functions. In this paper, a new cable-stripping robot for the 10 kV power system is introduced. The design of a live working cable-stripping robot that is appropriate for installing insulating rods is introduced, taking into account the working environment of 10 kV overhead lines and the structural characteristics of overhead cables. The robot is managed by an auxiliary remote control device. A cascade PID control technology based on the back propagation neural network (BPNN) method was developed, as the stripper robot's whole system is nonlinear and the traditional PID controller lacked robustness and adaptability in complex circumstances. To validate the structural feasibility of the cable-stripping robot, as well as the working stability and adaptability of the BPNN-PID controller, a 95 mm2 cable-stripping experiment are carried out. A comparison of the BPNN-PID controller with the traditional PID method revealed that the BPNN-PID controller has a greater capacity for speed tracking and system stability. This robot demonstrated its ability to replace manual stripping procedures and will be used for practical routine power maintenance.

Research on the Effect of an Air-Blown Interrupting Gap to Reduce the Rate of Lightning Tripping

The air-blown interrupting gap protection method is a self-energy interrupting method based on the concept of suppressing arc building by frequency continuation. In order to verify the effect of an air-blown interrupting gap to reduce the rate of line lightning tripping, in this paper, the protection principle of the air-blown interrupter gap is first described, and the action process simulated by COMSOL Multiphysics simulation software. Next, a frequency renewal test circuit is built for the test. Then, an arc-building rate calculation model and a lightning trip rate calculation model under the condition of an air-blown interrupting gap are established, and, finally, a 10 kV overhead line in Yunnan is selected for the verification of the calculation example. The results show the following: a gas blowing arc gap can be effectively extinguished in about 2.5 ms frequency arc and with no re-ignition phenomenon. Before and after the installation of the gas blowing arc gap line, the arc rate changed from 37.27% to 4.1%, respectively, and the lightning trip rate changed from 8.64 times/(40 thunderstorm days—100 km) to 0.337 times/(40 thunderstorm days—100 km), respectively. The decline rate was more than 95%, and in actual operation, it reduced the lightning trip rate enough to achieve good results.

Определение современных показателей надежности воздушных линий электропередачи 0,4-110 кВ

Reliability indicators for 0.4-110 kV overhead transmission lines need to be adjusted due to the lack of data on current values of reliability indicators for power system equipment. The authors’ analysis of offi cial statistical data on the number of emergency and scheduled outages in the branches of PJSC “Rosseti Tsentr” and “Rosseti Tsentr i Privolzhye” revealed deviations of the reliability indicators of electrical equipment of power systems and power grids from those presented in RD34.20.574. Also, the analysis showed that the standard presented no values of average downtime for planned outages of 0.4 kV and 6-10 kV overhead power lines. Reliability values of 0.4-110 kV overhead power lines were determined. Failure rate of 0.4 kV overhead lines made 6.2 to 7.04 year-1/100·km, of 6-10 kV overhead lines - 5.27 to 8 year-1/100·km. The “Orelenergo” branch, a failure fl ow of 35 kV overhead lines was 0.57 year-1/100·km, and 110 kV overhead lines - 2.83 year-1/100·km. The calculated value of the average restoration time for 0.4 kV networks was 1.88 h; for 6-10 kV networks - 3.1 h; 35 kV - 6.8 h; 110 kV - 9.5 h. The estimated average number of intentional outages for 0.4 kV networks was 0.1 year-1; for 6-10 kV networks 0.72 year-1; for 35 kV networks 0.4 year-1; for 110 kV networks 0.51 year-1. The average idle time of 0.4 kV overhead lines and 6-10 kV overhead lines amounted to 13.6 hours and 10 hours, respectively. The calculated average downtime of 35 kV overhead lines and 110 kV overhead lines amounted to 24.7 hours and 37.6 hours, respectively. The received data specify modern reliability values of electric 0.4-110 kV networks that can be used when planning measures on developing networks and reconstructing them.

Detection Method for Equivalent Ice Thickness of 500-kV Overhead Lines Based on Axial Tension Measurement and Its Application

Overhead line icing may threaten the operational stability of power grid. In this paper, a detection method for equivalent ice thickness of 500 kV overhead lines based on axial tension measurement was proposed. Firstly, according to the tension of insulator string when the transmission lines are not covered with ice, the horizontal distance from the lowest point of the transmission line to the tower on the side where the tension sensor is installed is calculated. Secondly, the state equation of the transmission line in the whole tension section is established. Then, the state equation is solved by iterative method. The initial ice thickness is taken as 0 mm. The ice thickness when the iteration value of tension <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> is equal to the measured value of tension <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> is taken as the equivalent ice thickness of transmission lines. The actual cases of single span transmission line and multi-span transmission line were used for verification and application effect analysis of the proposed method. The results show that the detected results of this method were consistent with the artificial ice observation values of typical 500 kV single span and multi-span transmission line cases. The accuracy of the proposed method can be further verified through finite element simulation analysis. The variation trends of the detected ice thickness is consistent with the icing conditions created by the meteorological factors during the same period, and can be verified by the icing photos captured on site.

The stress state analysis of lattice tower support for 330 kV overhead line using the “USL” software package

In conditions of market economy, overhead power transmission line (OPTL) support structures must be low-cost and of guaranteed quality, the manufacture of which will require a minimum amount of steel. Therefore, it is necessary to improve overhead line supports, which is possible by clarifying the forces in the support elements and when designing using numerical methods. In this article, a mode of deformation of a corner dead-end support of OPTL is analysed, which is considered a spatially multiple indeterminate open system with flexible joints. Attention is given to the basic problems that can occur in setting initial parameters and constructing design models for such structures. There are a number of problems connected with a refined specification of internal longitudinal stresses in the components of an OPTL structure. In designing, the joint operation of the lattice components of the support spatial pattern model is analysed, and the inclusion of stiffening diaphragms and diagonal element members in the operation on all four faces is taken into account. On the basis of the design and the extension of the results, the internal forces obtained and the ones specified in the components of the pattern OPTL support on the similar values of loads were thoroughly compared. When calculating the spatial model of an anchor-corner support as a result of the joint work of lattice elements, a decrease in internal forces in the elements of the spatial model is observed on average by 6.8%, compared to the forces determined in a typical overhead line support from the same load values. It has been established that it is quite acceptable to calculate overhead line lattice structures in the USL software package since the error in determining the forces in the rods is within 2% and the computer time consumption is less than in other software packages.

Accident analysis of 220, 500 kV overhead lines of the main power systems network

The statistical analysis of overhead lines (OHL) of the unified national power grid (UNPG) of the Central European part of the country for the previous 15 years is subjected to statistical analysis. The structure of the failure flow parameter (failure frequency) of 220 and 500 kV overhead lines with a total length of 17.6 and 8.5 thousand kilometers, respectively, is compared. It is shown that the last decade is characterized by the most favorable reliability characteristics. At the same time, a tendency was detected, when the parameter of overhead line failure flow became insignificantly dependent on the nominal voltage of the network. This fact makes us doubt the existing belief of specialists, according to which the specific (per 100 km) failure rate of overhead transmission lines decreases with the increase of the nominal voltage of the network. The above trend once again demonstrates the objective possibility of purposeful management of electric networks reliability.

Analysis of the technical condition and service life of 35-110 kV overhead power transmission lines in the Oryol Region

The assessment of the technical and operational characteristics of overhead transmission lines of voltage classes 35-110 kV in the Oryol Region has been carried out in accordance with the methodology presented in the order of the Ministry of Energy of the Russian Federation dated July 26, 2017 No. 676; their service life was determined according to STO 56947007-29.240.01.053-2010. The analysis of the length of overhead lines and the types of conductors used has taken place using support-by-support schemes. In the construction of 35 kV lines, steel-aluminum wire (sectional area - 70 mm) is mainly used, the length of which is 1,358,456 km, and 110 kV overhead lines are made using an AS-120 conductor (1,094 km). Overhead transmission lines are characterized by high indicators of technical condition, since 40 % of lines of voltage class 35 kV and 53 % of lines of voltage class 110 kV are in very good technical condition with a wear rate of no more than 15 %. The study has found that 71 % of overhead lines with a voltage of 35 kV and 85 % of lines with a voltage of 110 kV have been in operation for more than 35 years; at the same time, due to the implementation of a timely strategy for maintenance and repair, the lines are characterized by high indicators of technical condition.

Investigation of line surge arresters application to the 150 kV system of Rhodes

• The application of line surge arresters to 150 kV overhead lines is investigated. • The required energy absorption capability of line surge arresters is determined. • Non-gapped line arresters and externally gapped line arresters are compared. • Surge arrester installation configurations are evaluated for critical lines. • Lightning performance improvement of a critical 150 kV overhead line is quantified. This paper investigates the application of Line Surge Arresters (LSAs) to 150 kV double-circuit overhead lines through ATP-EMTP simulations. The 150 kV lines under study are the backbone of the autonomous electrical system of Rhodes island in southeastern Aegean Sea, Greece. Hence, lightning-related insulation flashovers causing outages of these lines may lead to a blackout of this isolated system. In this work, both Non-Gapped Line Arresters (NGLAs) and Externally Gapped Line Arresters (EGLAs) are evaluated. Two installation configurations with 3 and 6 LSAs per tower are considered protecting one circuit and both circuits of the line, respectively. Simulations were performed for both lightning strikes to phase conductors and tower; these may cause shielding failure flashover and backflashover, respectively. The conducted current through the LSAs and the voltage at their terminals are computed, enabling the estimation of the energy stressing the LSAs. The effects of the lightning current time to half value, the phase angle of the operating voltage, and the power frequency ground resistance of towers are assessed. The required LSA energy absorption capability is determined. The lightning performance of a critical overhead line of the Rhodes 150 kV system is estimated and its improvement due to LSA installation is quantified.

Simulation analysis of the effect of single-chamber double-line pipe jacking through different soil materials on surface uplift and subsidence.

This article is based on the relocation project of the 330 kV overhead line in Xi’an, China. In this paper, the soil settlement under different jacking depths was calculated by using the modified Peck’s formula. Meanwhile, by modeling in ABAQUS, the jacking process of a single-chamber double-line large diameter pipeline under different soil conditions was simulated, and the ground deformation data under the different simulated working conditions were obtained. The results of the two methods were compared with the construction monitoring results, and it was found that the finite element simulation results were closer to the actual results. The control variable method was used in the analysis of the surface soil deformation law to analyze the effect of different soil parameters and pipe jacking depths on surface soil deformation. Finally, the best soil conditions applicable to single-chamber double-line large diameter pipe jacking construction were obtained through comparative analysis. The results show that (1) when using double-line construction, the maximum surface settlement under different soil conditions is located 11–15 m from the centerline of the soil above the pipeline, the minimum settlement location is inside the isolation pile, and with the increase in jacking distance, the settlement at the same section of the surface will gradually decrease and finally produce a small uplift. (2) In the first jacking, the settlement of powder clay is the largest, and the maximum settlement points in the surface section are more distributed. The maximum settlement value is approximately 11.66 mm. The settlement of powder soil is the smallest but produces a certain uplift deformation, and its maximum settlement is more concentrated in the surface section. After the comparison of deformation and soil parameters, loess-like soil is more suitable for single-compartment double-line large diameter pipe jacking construction. (3) When the top pipe burial depth changes, the greater the burial depth is, the smaller the settlement but the greater the lateral influence range. In the soil parameters, the modulus of elasticity only changes 3 MPa, and the settlement change value is approximately 5 mm. By changing the parameters, it can be obtained that the larger the modulus of elasticity of the soil is, the smaller its deformation. The larger the internal friction angle of the soil is, the smaller its deformation, but the maximum value of settlement change is only 1.7 mm, which means that the change in the internal friction angle has little effect on the soil deformation.