Overhead Lines Research Articles

A Novel Approach to Dynamic Line Rating Calculation

In order to adjust the electric power network to today’s trends—such as the charging of electric vehicles, design of the Internal Electricity Market (IEM), headway of renewable energy sources, etc.—the demand for flexible network solutions is increasingly significant. Dynamic line rating (DLR) technology offers a flexible solution for the uprating of overhead lines. Moreover, the DLR methodology can be used in a wider system approach in order to establish a line management system, including functions such as ice prevention subsystems or the real-time tracking of clearances. Therefore, the extension possibilities and operational features of DLR-based systems have been extensively researched in the last few years, which is also confirmed by the high number of pilot projects funded for research and development on the topic of DLR. The key question during the implementation of a DLR system is the obtainable operational safety of such a system. This mainly depends on the installation places of the field equipment and the accuracy of the line rating calculation models. The aim of this article is the comparison of the so far available international line rating calculation models and also to propose another way for the determination of the real-time line rating. Moreover, laboratory measurements and case studies are presented for the confirmation of the proposed model’s reliability.

Long‐term and multi‐objective maintenance scheduling of medium voltage overhead lines based on LP metric method

AbstractPlanning maintenance of medium voltage overhead lines is one of the most important issues in the studies on power distribution network, which will prevent and reduce unwanted interruption. In this paper, long‐term maintenance of medium voltage networks was planned by multi‐objective function, including an extended mixed‐integer linear model to optimize costs, energy not supplied (ENS), and average interruption duration index (SAIDI). In addition, the uncertainty about the annual growth rate of the load, the increase in the cost of goods and services and the increase in the selling price of energy as well as various constraints are all included in the desired objective function, which is one of the main innovations of this paper compared to other published studies. To apply the uncertainties, information gap decision theory (IGDT) has been used, and to solve the objective functions, LP‐Metric method has been used. The proposed method was implemented on the standard 11‐bus RBTS network by MATLAB and GAMS. The results showed that three different long‐term maintenance plans proposed here lead to the optimization of the annual maintenance costs of network, reduction in ENS and interruption, and increase in the reliability of the network based on the uncertainty of each feeder.

Thermal model of DC conductors for railway traction networks: A hosting capacity assessment

In this paper, the authors have adapted existing thermal models for the calculation of conductor temperature for use in electrical distribution systems for railway applications in multi-train environments. For this purpose, the authors have used existing standards such as IEEE 738 for overhead lines and have proposed a resolution methodology based on the difference equation model for cables. The authors have opted for a simplified method since the priority in this case is the resolution in systems with multiple stations, lines, and trains. For this same reason, they have chosen to decouple the electrical and thermal calculations so that the electrical variables calculated through load flows constitute the input to the thermal calculation problem. The paper reviews the existing formulation and proposes models for specific use in railway applications in a multi-train environment. A detailed analysis of the results obtained in a real case study is presented as a validation element.

Active Displacement Control of Pantograph-catenary System for a Half-body Railway Model

The pantograph is an essential component that provides electrical contact between the overhead wires and the electric train. The quality of the current collection in high-speed trains is directly influenced by the mechanical interaction between the pantograph collector head and the overhead contact line. To overcome these challenges and improve pantograph performance, researchers and engineers have explored innovative solutions, including the introduction of active control mechanisms. Excitation by the vehicle is one of the normal disturbances in the dynamic interaction of the pantograph and the overhead line. The vertical effects of vehicle-track vibrations on the interaction between the pantograph and the overhead contact line have not yet been adequately researched. To fill this research gap, this study establishes models for both the pantograph-catenary interaction and the vehicle-track system. In this study, the performance of the modified Skyhook-Proportional-Integral-Derivative (PID) controller was investigated for a half-body of a railway pantograph-catenary system. Track irregularities such as step, sine, and random were applied to perturb the suspension system. The performance of both passive and active systems was investigated by considering the track irregularities as a basis. The root mean square analysis (RMS) found that active displacement control of pantograph-catenary systems for a half-body railway model equipped with modified Skyhook-PID controllers performed better than the passive systems. In summary, the future experimental approach for active half-body railway model could incorporate this simple modification of the Skyhook-PID controller.

Diagnostics of Internal Defects in Composite Overhead Insulators Using an Optic E-Field Sensor.

Composite insulators for high-voltage overhead lines have better performances and are lighter than traditional designs, especially in heavily polluted areas. However, since it is a relatively recent technology, reliable methods to perform live-line diagnostics are still under development, especially with regard to internal defects, which provide few external symptoms. Thermal cameras can be employed, but their use is not always straightforward as the sun radiation can hide the thermal footprint of internal degenerative effects. In this work, an optical E-field sensor has been used to diagnose the internal defects of a set of composite insulators (bandwidth 200 mHz-50 MHz, min. detectable E-field 100 V/m). Moreover, a modelling activity using finite elements has been carried out to identify the possible nature of the defects by comparing experimental E-field profiles with those simulated assuming a specific defect geometry. The results show that the sensor can detect the presence of an internal defect, since its presence distorts the E-field profile when compared to the profile of a sound insulator. Moreover, the measured E-field profiles are compatible with the corresponding simulated ones when a conductive defect is considered. However, it was observed that a defect whose conductivity is not at least two orders of magnitude greater than the conductivity of the surroundings remains undetected.

EVALUATION OF CLOUD TO GROUND FLASH DENSITY OF 150 KV TRANSMISSION LINE BETWEEN PARIT BARU SUBSTATION AND SENGGIRING SUBSTATIO

SUTT is a high voltage overhead line with a power of 70 kV - 150 kV to distribute electric power from the generating center to the substation or from substation to substation. The purpose of this study was to obtain modeling of lightning strike density on the 150 kV transmission line between Parit Baru substation and Senggiring substation using geostatistical approaches, namely IDW methods (Inverse Distance Weighted). In identifying the level of vulnerability to lightning strikes, Cloud to Ground lightning event data (2018–2020) is used. The aim of this research is to obtain the density pattern of lightning strikes on the 150 kV transmission line between the Parit Baru substation and the Senggiring substation. The process in ArcGIS 10.8 software aims to obtain lightning strike density and display the results of the lightning strike density map. Based on the results of data processing for 3 years, the highest density of lightning strikes occurred in 2019 in Segedong District at 54.52 strikes/km². Meanwhile, the lowest density of lightning strikes occurred in 2018 in East Mempawah District, amounting to 2.86 strikes/km². Based on the lightning strike density map per grid on the 150 kV transmission line between Parit Baru substation and Senggiring substation for 3 years, the results obtained for the highest lightning strike were 36 strikes/km² while for the lowest strike it was 1 strike/km². From this research, it was found that there were 15 transmission towers that passed a high density of lightning strikes with a strike range of 25–36 strikes/km² and the highest lightning strike occurred at tower number 31, number 30, and number 29, amounted to 36 strikes/km².

A Test System for Transmission Expansion Planning Studies

This paper introduces a 17-bus 500 kV test system intended for transmission expansion planning (TEP) studies. The overhead lines used in the system are based on an actual 500 kV transmission line geometry. Although several test systems have been developed for various forms of power system analysis, few are specifically tailored for TEP studies at the transmission voltage level, as opposed to the distribution voltage level. Current test systems for TEP studies are limited to single loading conditions only for normal operating conditions, and the majority of these systems are intertwined with issues related to the energy market or devised specifically for integrating new generations and loads into the existing power systems. However, ensuring a test system satisfies both voltage drop and line loading criteria during both normal and all single contingency operations is crucial in TEP studies, and addressing these issues under contingency conditions poses notable challenges. Moreover, practical TEP scenarios involve varied loadings, including peak load and dominant loading (60% of peak load) scenarios, while the existing test systems are configured solely for single loading conditions. To address these technical gaps, this paper introduces the 17-bus test system operating at a transmission voltage level of 500 kV, meeting technical requirements under normal and all single contingency operations for both peak load and dominant load scenarios. Detailed specifications of the proposed test system and load flow analysis at both normal and contingency conditions for different loading conditions are presented. This test system serves as an invaluable resource for TEP studies.

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 Decision Tree Based Ultra-high-speed Protection Scheme for Meshed MMC-MTDC Grids with Hybrid Lines

The reliable operation of modular multi-level converter based multi-terminal high voltage direct current (MMC-MTDC) grids requires high-speed and selective DC line protection. A single-ended protection technique is proposed for MTDC grids with offshore wind farms and hybrid lines that involve overhead lines and submarine cables in series. Positive and negative poles’ currents at one end of each line section are analyzed using discrete wavelet analysis (DWA). To classify fault type and identify fault zone, a fine decision tree is supplied with an energy index and the envelope slop of detail 1 coefficient (D1) obtained from DWA. Only 0.2 ms following the fault inception are needed for calculating the energy index and the envelope slope to perform relay functions. The approach was tested on a three-terminal two-poles ±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document} 400 kV MMC-MTDC model. The simulation results validate the effectiveness of the suggested protection technique under various fault scenarios, even with up to 200 Ω fault resistance. The proposed technique is not only able to detect the faulty line, but also it identifies overhead line faults and submarine cable faults for hybrid type lines. Moreover, the proposed technique is not affected by wind power injection changes, AC faults, or data noise. The simulated model was produced in the MATLAB/Simulink platform.

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.

Passive Safety Assessment of Railroad Trains in Moose Herd Collision Scenarios

Moose herd–train collisions represent one of the potential hazards that railway operations must contend with, making the assessment of passive train safety in such scenarios a crucial concern. This study analyzes the responses of bullet trains colliding with moose herds and investigates the influence of various factors under these conditions. To achieve this goal, a multibody (MB) model was developed using the MADYMO platform. The displacement of the moose’s center of gravity (CG) was employed to assess the safety boundaries, while the relative positions between the wheels and rails were used to evaluate the risk of derailment. The findings revealed that the collision forces exhibited multi-peak characteristics that were subsequently transmitted to the wheel–rail contact system, resulting in disturbances in the relative positions of the wheels and rails. However, these disturbances did not reach a level that would induce train derailment. Furthermore, larger moose herds exhibited higher throw heights, although these heights remained within safe limits and did not pose a threat to overhead lines. The primary safety risk in moose–train collisions stemmed from secondary collisions involving moose that had fallen onto the tracks and oncoming trains. This study offers valuable insights for enhancing the operational safety of high-speed trains and safeguarding wildlife along railway corridors.

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.

Capacitor Switching Techniques

Capacitance switching applications involve not only interrupting capacitive currents, but also the energizing of capacitor banks, cables and overhead lines. The interruption of a capacitive current can cause dielectric problems for the switching device. The high inrush currents can cause damage to the capacitors of the capacitors bank and to weld the contacts of the switch together. The problems of the capacitive inrush currents and ways to reduce the magnitude of the inrush current, have been chosen for analysis in this paper.

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.

Field Measurement Based PLS Model for Dynamic Rating of Overhead Lines in Wind Intensive Areas

This paper presents results of lab tests, field measurements and mathematical modelling for the Dynamic Rating (DR) of Over Head Transmission Line (OHTL) in a wind intensive area. In this paper, DR is done by developing a statistical line model. This model is based on Partial Least Squares (PLS) multi regression. DR provides extra capacity to the line, over the traditional seasonal static rating, which makes it possible to defer the need for reinforcement the existing network or building new lines.

Experimental study of a temperature measurement system for an overhead power line using sensors based on TFBG

This article presents the use of an inclined fiber sensor Bragg grid to control the extension of wires in overhead lines. An aspect of the technological novelty of the project is the development of an innovative optoelectronic system for monitoring and diagnosing the condition of building structures based on a combination of conventional Bragg gratings. The lighting power sensor is installed directly on the controlled transmission of the power line in the form of fittings with a copper plate. A photosensitive multimode optical fiber is attached to the copper plate, at the end of which an inclined fiber Bragg grating is fixed, connected to a multimode optical fiber using a fiber-optic connector through an optical connector. An ultraviolet excimer laser and a light power detector are connected to a fiber-optic connector. The study showed that by selecting the appropriate mechanical parameters of the extension transformer, taking into account the optical parameters of the sensor, and using a special filter, the optical-mechanical system can be configured in the required range to control the sagging of the overhead line wire. During measurements to simulate the operation of a power line wire, the temperature was forced to vary in the range of 10-60°C. This led to the lengthening of the test wire from 38.987 m to 49.275 m; the error was within 4%. The deflection range depends on the distance between the supports, the type of wire, and its actual length in the span, which actually determines the deflection.

Overvoltages caused by direct lightning strokes to a hybrid overhead line

This paper presents an analysis of the overvoltages caused by direct lightning strokes to a hybrid overhead line with 138 kV, 13.8 kV, and 220 V circuits. The primary focus is on medium voltage line overvoltages and their dependence on key parameters, including ground impedance, soil resistivity, stroke current front time, conductor characteristics, lightning channel impedance, insulator capacitance, conductors' sags, and tower surge impedance. Using specific models for the transmission tower and high-voltage insulators, validated through laboratory tests and EMTP simulations, critical currents are determined for varying soil resistivity and impulse impedances. The analysis confirms the line robust performance against stroke-induced backflashovers.

Innovative Engineering Solutions for Short Neutral Section Maintenance Reduction in Railway Overhead Lines

This work addresses the challenges associated with the development of short neutral sections (SNS) for overhead lines of high-speed moving trains. A crucial function of a short neutral section is to provide electrical isolation between the different phases of AC traction. These sections are typically located in proximity to the traction substation and sectioning posts. The current SNS design presents several issues, including pantograph arcing, wear and tear of the overhead line system, and the need for manual rotation during periodic maintenance. To address these challenges TRIZ is used, a problem-solving methodology that leverages inventive principles to generate innovative solutions. The work outlines the use of several TRIZ tools and techniques, including the Interaction Matrix, Functional Analysis, Function-Body Diagram (FBD), Trimming, and the Contradiction Matrix [1]. With the application of these tools, the author presents several potential solutions for improving the SNS design to eliminate periodic maintenance and services. One proposed solution involves the use of a segmented overhead line system with an insulating cylinder-shaped discrete insulator to ensure smooth contact of the pantograph. Another solution involves the use of a twisted strip-based insulator to replace linear motion with rotating movement, eliminating the need for manual rotation. The work emphasizes the importance of considering various factors, such as design, material, wear rate, maintenance, and creepage distance, when evaluating the feasibility of these solutions. By leveraging TRIZ to generate innovative solutions, the author demonstrates the potential of this methodology to drive innovation and overcome complex challenges in the development of short neutral sections for high-speed rails.

Prediction method for response characteristics parameters of isolated-span overhead lines after ice-shedding based on finite element simulation and machine learning

In response to the problem of insufficient research on the prediction for response characteristics parameters of isolated-span transmission lines under various ice-shedding modes, study on the prediction for ice-shedding response parameters of isolated-span overhead lines is conducted in this paper based on finite element simulation and machine learning. Firstly, the finite element simulation model of isolated-span overhead line is established and verified. Seven model input parameters are determined by considering 12 typical ice-shedding modes and ice-shedding labels are introduced. Six key output parameters reflecting the electrical and mechanical characteristics of the ice-shedding transmission line are obtained by feature extraction. Secondly, the output parameters of the ice-shedding transmission line under different input parameter conditions are obtained by using the finite element simulation method. A total of 1400 sets sample data are constructed. Then, four typical regression prediction models of BP (Back Propagation Algorithm), RBF (Radial Basis Function Algorithm), SVM (Support Vector Machine Algorithm) and RF (Random Forest Algorithm) are established to predict the key output parameters of ice-shedding transmission lines. Finally, the optimal prediction model for ice-shedding response characteristics parameters of isolated-span transmission lines is selected and the application effect is analyzed by actual ice-shedding case. It is found that the RF prediction model is the optimal prediction model among the four regression prediction models. The prediction method for ice-shedding response characteristics parameters of isolated-span transmission line proposed in this paper can accurately predict the response characteristics parameters of ice-shedding transmission lines which can provide some references for the safe operation of isolated-span transmission lines in heavy ice areas.

Study of operation of a polymer insulator under uniform and non-uniform contamination

RELEVANCE. Suspended insulators, the technical condition of which largely determines the reliability of power supply to consumers of different categories, are one of the most damaged elements of overhead power transmission lines [1-2]. This is primarily due to the fact that during their operation, insulators are exposed to various climatic conditions that have a direct impact on their insulating properties. Moreover, precipitation, such as rain, fog or dew, has the greatest impact precisely in combination with various solid, liquid and gaseous particles deposited on the insulator surface from the air, and forming a layer of surface contamination. Wetting this layer increases the electrical conductivity of the entire overhead line insulation structure and reduces its insulating capacity. Study of influence of dampening of contaminated surface of suspended insulation on their discharge characteristics is an urgent scientific task. The solution of this task enables to develop the existing understanding of the mechanisms of formation and development of discharges on the contaminated and wetted surface of insulation and to formulate the appropriate diagnostic attributes applicable to control the condition of the overhead power line insulators. OBJECTIVE. To carry out laboratory research aimed at studying the behavior of suspended high-voltage polymer insulators of overhead power lines when they are moistened. To formulate appropriate diagnostic attributes applicable for control of condition of suspended insulators of overhead power lines during their operation. METHODS. At the solution of the posed problem experimental methods of research, consisting in simulation of work of the contaminated polymeric insulator in the atmosphere of a pure fog with application of the special experimental installation developed by the authors of this article were applied. RESULTS. As a result of laboratory research, by continuous registration of leakage current values, as well as signals coming from the remote sensor, characteristic features of contaminated insulator humidification were revealed, which can be used as diagnostic signs in the process of their operation.