kV Overhead Transmission Lines Research Articles

Improving electric field stress using grading ring devices for insulated cross-arm

Insulated cross-arms (ICA) allow for the compaction or enhancement of transmission lines. This study presents a comprehensive approach to designing and evaluating insulated cross-arm (ICA) grading devices to control electric fields for insulated cross-arms on a 132 kV lattice tower. A ring-shaped grading device is designed for the low voltage (LV) end of the insulator. A novel grading device is designed for the high voltage (HV) end—a single piece that controls the field for all four ICA members. Finite element analysis (FEA) simulations assess the electric field stress near the HV and LV ends of the ICAs, ensuring that it remains below the critical threshold of 18 kV/cm and effectively improves electric field stress at both ends of compression insulator by 70 % electric field stress at LV end and 80 % improved at HV end. The study outlines a thorough design methodology and provides valuable guidelines for utilising FEA in developing complex geometries. By adopting this approach, the researchers aim to enable the adequate compaction and upgrading of new and existing 132 kV overhead transmission lines, ultimately contributing to optimising power grid infrastructure. The findings of this study demonstrate the importance of integrating comprehensive design strategies and advanced simulation techniques to enhance the reliability and performance of ICA.

Evaluation of the Backflashover Performance of a 150 kV Overhead Transmission Line Considering Frequency- and Current-Dependent Effects of Tower Grounding Systems

Evaluation of the Backflashover Performance of a 150 kV Overhead Transmission Line Considering Frequency- and Current-Dependent Effects of Tower Grounding Systems

Integration of Solar Photovoltaic Power Plants Into the Power Transmission System of Bosnia and Herzegovina Load and Voltage Conditions Analysis

Abstract Governments in the region are actively trying to decentralize production in the energy sector by encouraging the construction of power plants using renewable energy resources. The Network Code [1] and the Connection Regulation [2]-[4] define the procedure for issuing connection conditions to the power transmission network in Bosnia and Herzegovina. This paper will demonstrate the necessary approach to assessing the possibilities of connection and placement of the produced power and energy at a specific connection point in the early stages of planning, using the example of an 80 MW photovoltaic power plant planned for construction in the municipality of Tomislavgrad. The connection of the power plant is planned on a 110 kV voltage level network, by connecting it to the target 110 kV overhead transmission lines, following the principle of input-output.

A Dynamic Load Increasing Method for 220 kV Overhead Transmission Lines and Application

With the continuous development of China’s economy, the demand for electricity in society is increasing year by year, and it is necessary to continuously strengthen the construction of transmission capacity. This article aims to develop a terminal monitoring device that can monitor the status of transmission lines and the environment, analyze the monitoring data of overhead line status and micrometeorological data, and, based on the prediction model of the current carrying capacity of transmission lines, fully tap the power supply potential of transmission lines, which is of great significance for improving the transmission capacity of transmission channels.

Weather dependency of corona losses on 330 kV overhead transmission lines

This paper presents an analysis of how corona losses on transmission lines depend on weather conditions in their vicinity. Two years of synchronized phasor measurement data has been collected to monitor corona losses over a longer period of time. From the same time period, both hourly and 10 min weather monitoring data has been obtained for comparison. The dependence between various weather parameters and corona losses is presented with graphical data analysis. In addition, feature importance methods have been applied to rank the weather parameters and determine which of them have the largest influence on the occurrence of significant corona losses. The results presented in this paper are directly applicable for transmission systems operators for adequate planning of system operation.

Selection of Foundation Types for Mechanized Construction of 220 kV Overhead Transmission Lines in Mountainous Areas Suitable for Fujian Province

The construction of overhead transmission lines in mountainous areas poses a significant challenge when it comes to foundation construction. The type of foundation selected in these areas has a direct impact on equipment selection and access road planning. Fujian Province, located on the southeastern coast of China, is predominantly hilly and mountainous. Therefore, selecting an appropriate foundation for overhead transmission lines is crucial for successful mechanized construction of transmission lines in this region. In this study, we aimed to enhance the economy of mechanized construction of the foundation of the 220 kV overhead transmission lines in Fujian Province. We analyzed the typical geological conditions and foundation reactions in the area and compared the construction costs of mechanical pile foundations, mechanical digging foundations, and rock anchor foundations. The results show that the mechanical pile foundation requires the least amount of concrete when the foundation reaction of the 220 kV suspension tower is less than 1700 kN and the foundation reaction of the 220 kV tension tower is less than 1300 kN. Additionally, the quantity of the rock anchor foundation is less than that of the digging foundation. In terms of cost, the rock anchor foundation is the most economical, followed by the mechanical pile foundation and then the digging foundation.

Operation Recommendations for Tension Joints and Clamps on a 63 kV Overhead Transmission Line Conductor Based on Experimental Tests

This study provides the operation recommendations for the tension fittings used on a 63 kV overhead transmission line conductor based on experimental tests. In this way, the tension fittings, including the dead-end clamp, the mid-span joint, and the repair sleeve, are assembled on the lynx conductor under different faulty and healthy assembly conditions in the laboratory. The lynx conductor is one of the widely used conductors in the 63 kV overhead power lines. The electric current injection test, along with thermal imaging and also tensile test, are conducted on the studied samples. The results show that the surface temperature of the lynx conductor is higher than the surface temperatures of the dead-end clamp and mid-span joint under normal and overload current conditions. Also, the crimping pressure of the aluminum and steel pipes less than the standard value, the crimping length of the steel cores of conductor less than the standard value, and the crimping length of the aluminum pipes more than the standard value can lead to a developmental defect which should be repaired or replaced at the first opportunity of the transmission line service outage. The repair sleeve is under more thermal stress than the dead-end clamp and mid-span joint, even in the standard assembly condition. A slight temperature difference of a repair sleeve compared with the same type fitting may be a severe operating condition. Also, the use of two consecutive repair sleeves to cover the conductor cut strands is not recommended. Furthermore, the loose connection of bolts at the junction of the jumper terminal to the dead-end clamp causes a very high temperature which should be repaired immediately. If the temperature difference between two defective and healthy dead-end clamp or mid-span joint is more than 13 °C, a critical defect is diagnosed; however, the temperature difference between two repair sleeve more than 7 °C indicates a critical operation condition for defective one.

Fast Detection of Current Transformer Saturation Using Stacked Denoising Autoencoders

Malfunctions in relay protection devices are predominantly caused by current transformer (CT) saturation which produces distortion in current measurements and disturbances in power system protection. The development of deep learning in power system protection is on the rise recently because of its robustness. This study presents a CT saturation detection where the secondary current becomes distorted. The proposed scheme offers a wide range of saturation detection and consists of a moving-window technique and stacked denoising autoencoders. Moreover, Bayesian optimization was used to minimize the difficulty of determining neural network structure for the proposed approach. The performance of the algorithm was evaluated for a-g faults on 154 kV and 345 kV overhead transmission line in South Korea. The waveform variation has been generated by PSCAD for different scenarios that heavily influence CT saturation. Moreover, a comparative analysis with other methods demonstrated the superiority of the proposed DNN method. With the proposed algorithm to detect CT saturation, it significantly yielded high accuracy and precision for CT saturation detection which were approximately 99.71% and 99.32%, respectively.

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.

Experimental Study on Ultrasonic Detection Method of Ice Thickness for 10 kV Overhead Transmission Lines

Transmission-line icing is a serious threat to the security safe and stable operation of power systems. The icing monitoring of transmission lines is of significance for the prevention of freezing disasters in power systems. However, the lack of effective ice detection methods has brought great trouble to the safe operation for 10 kV overhead transmission lines in freezing weather. To tackle this problem, a method for detecting ice thickness for 10 kV overhead transmission lines based on ultrasonic detecting technique is proposed in this paper, in which the distance from the ultrasonic sensor to the line changed by transmission lines ice-coating and the distance difference before and after ice-coating detected by ultrasonic being the ice thickness. An ultrasonic detection platform for ice thickness on the steel rod to simulate the line icing is established. The calibration experiment with the effect of distance, temperature, and wind velocity on the ultrasonic is carried out, and the experiment with ice thickness on the steel rod detected by the ultrasonic is carried out. Furthermore, the effect of ice shape on the detection is studied, and the reason for the large error is analyzed when the number of bulges on the ice surface is large. The results show that the relative error of ice thickness obtained by the method proposed in this paper is less than 10% under conditions of uniform ice and relatively smooth ice surface, compared with vernier caliper measurements. An improved method for ice thickness detection using the trough time as the ultrasonic echo signal time is proposed when the number of bulges on the ice surface is large, and the relative error value of the improved method is verified to be less than 5%.

Influence of a lossy ground on the lightning performance of overhead transmission lines

• Accurate lossy ground representation impacts lightning overvoltages simulation. • Carson's classic formulation may lead to inaccuracies for high-resistivity soils. • Accurate lossy ground representation in simulations leads to higher TLs outage rate. • An increase up to 15% in TL outages was found when ground is accurately represented. This paper investigates the impact of incorporating both displacement currents and frequency-dependent soil parameters in the calculation of the ground-return impedance for the determination of the backflashover rate of 138 kV and 230 kV overhead transmission lines due to direct lightning strikes. This is done by considering the Sunde's formulation for calculating the ground-return impedance, which is incorporated in a time-domain simulator using an alternative implementation of Marti's transmission line model. The obtained results show that the peak of the lightning overvoltages computed considering Sunde's formula, along with frequency-dependent soil parameters, leads to higher amplitudes in comparison with those simulated using the classical Carson's formula, which neglects the frequency dependence of soil parameters and assumes conductive currents in the soil much larger than displacement currents. This effect is more pronounced in high-resistivity soils and leads to an increase in the line backflashover rate within 4-6%, 7-12% and 9-15% for 1000 Ωm, 5000 Ωm and 10000 Ωm soils, respectively, considering 138 kV and 230 kV lines, and assuming a typical median first stroke lightning current. Analyses performed with slow and fast first stroke currents confirm the trend of increase of the backflashover rate with the consideration of Sunde's formula.

The Health Index Analysis on Asset Management and the Influence of Electricity and Environmental Safety Aspects on Overhead Transmission Line 150 kV Anyer – Asahimas

The availability and reliability of electrical energy has become the backbone of society, so periodic maintenance needs to be carried out to avoid short breakdowns and technical malfunctions as well as to improve electrical and environmental safety. Overhead transmission line is an important part of the transmission network and their health status is an important foundation for ensuring the reliable supply of electricity to the power grid. The health index (HI) is a value that reflects the health status of high-voltage transmission lines obtained by combining the normalization of component ratings on certain parameters and calculation methods. This study shows that the condition of assets, electricity and the environment have an effect on determining the soundness index of the Anyer-Asahimas 150 kV overhead transmission line and can be a guide for its maintenance. The final health index value shows 92.8% meaning that the transmission is not only safe in terms of equipment but also safe in terms of electrical and environmental safety aspects.

A dagging‐based deep learning framework for transmission line flexibility assessment

AbstractUncertainty in renewable energy generation, energy consumption, and electricity prices, as well as transmission congestion, pose a number of problems in modern power grids, necessitating stability on the supply, grid, and demand sides. Grid‐side stability can be achieved by dynamic line rating (DLR) forecasting, which reliably predicts the overall current carrying potential of overhead transmission lines. Long short‐term memory proved beneficiary in this field, owing to its ability to learn highly variable and uncertain data. To empower this network to tackle the non‐stationary nature of meteorological parameters, a novel machine learning (ML) architecture based on Dagging technique is proposed and tested on the data collected from a 400 kV overhead transmission line. Simulation results corroborate that the proposed Dagging‐based stacked LSTM can successfully handle the non‐stationary issue and outperform the decomposition‐based technique, as the state‐of‐the‐art algorithm, for various forecasting horizons. The results confirm the generalizability of models with an application in forecasting DLR over the line without utilizing additional sensors and communication networks. Moreover, the proposed model is compared to several ML architectures, including support vector machines (SVM), random forest (RF), and multi‐layer perceptron (MLP) in a comprehensive benchmark study. The introduced algorithm outperforms MLP by 3.4%, RF by 9.4%, and SVM by 6.7% in terms of average prediction accuracy.

Hierarchical Extreme Learning Machine Enabled Dynamic Line Rating Forecasting

Dynamic line rating (DLR) is a technology introduced to rectify an overhead line's current carrying capacity based on climatic conditions. Reducing congestion costs, increasing the penetration of renewable energy, and network stability are the most important benefits of this modification. The DLR forecasting is a significant issue and can be very useful in network management decisions for real-time and day-ahead. So far, however, very few studies have talked about the literature on day-ahead DLR forecasting. This article develops various DLR forecasting models based on historical meteorological data and machine learning techniques. Accordingly, multilayer perceptron, group method data handling, support vector regression, back-propagation neural network, extreme learning machine (ELM), and hierarchical ELM (H-ELM) techniques compete for short-term DLR forecasting of two 400 kV overhead transmission lines, installed in the Khaf and Ghadamgah regions in Iran. The meteorological parameters such as air temperature, wind speed, wind direction, and solar radiation in the studied areas are utilized as input variables for selected methods. Different evaluation indicators assessments the forecasting results of each technique. Finally, evaluations emphasize the effectiveness and capability of the H-ELM method with the lowest forecasting error values and the highest correlation coefficient value compared to other methods. Experiments exposed the DLR forecasting models' generalizability at various points of the line without the extension of monitoring devices and communication infrastructures.

Analysis of ACCC failure of composite core glass transition temperature reduction due to brittle damage

The failure analysis of the Aluminum Conductor Steel Reinforced (ACSR) was often based on conventional failure methods such as strength and fracture, and the failure analysis of the Aluminum Conductor Composite Core (ACCC) usually followed the analysis methods of the ACSR. This research proposed a new ACCC failure mode based on the glass transition temperature (Tg) of composite materials. In this paper, a fracture accident of a 500 kV overhead transmission line was discussed. Firstly, impact test found that composite core of the ACCC was more brittle than steel core of the ACSR, and the brittle damage of the composite core was inferred as the cause of the accident in combination with fracture analysis. Then, thermal-structural coupling analysis showed that the axial stress of aluminum wires increased to 33 MPa after the brittle damage of the composite core. Subsequently, thermoelectric coupling analysis showed that the operating temperature (T) of conductor was raised to 151 °C after the increment of the axial stress of the aluminum wires. Finally, in dynamic mechanical analysis, it was shown that the Tg of faulty composite core was reduced to 146.3 °C. According to investigation, the T of conductor was greater than the Tg of epoxy resin in the faulty composite core, resulting in a decrease in the tensile strength of the composite core, which eventually led to the ACCC failure. The failure mechanism proposed in this paper can provide a reference for the prevention and maintenance of ACCC lines in power grid system.

Comparative study of 220 kV overhead transmission lines models subjected to lightning strike simulation by using electromagnetic and alternative transients program

Introduction. In high voltage networks intended for the transport of electrical energy, lightning can strike an electric line striking either a phase conductor, a pylon or a ground wire, causing significant overvoltage on the transmission lines classified as stresses the most dangerous for transformer stations and electro-energy systems in general. Modeling transmission lines becomes more complicated, if the frequency dependence of resistance and serial inductance due to the effect of lightning strike in the conductors and in the earth is considered. The difficulty increases the fact that the parameters of the line can be defined and calculated only in the frequency domain, while the simulation of transients is wanted to be in the time domain. Problem. Several models (J.R. Marti, Bergeron, nominal PI, Semlyen and Noda) exist for the modeling of transmission lines, the Electromagnetic Transients Program/Alternative Transient Program software (EMTP/ATPDraw) gives the possibility to choose between these models which is delicate due to the fact that we do not have experimental results to validate and justify the choice among the models available in the software. In this context, practical value: the overhead transport line OAT-El Hassi (220 kV) of the city of Sétif located in the north east of Algeria is used for the modeling of lightning strike by using the EMTP/ATPDraw software. Originality. A comparative study of the investigation of a lightning strike on an existing high voltage transmission line by different models of existing lines in the EMTP/ATPDraw software library of this software. Results. It was concluded that the choice of the model of the line is very important given the accuracy and quality of the curves of the voltage presented at the different calculation points.

ВИЗНАЧЕННЯ СКЛАДОВИХ ВТРАТ АКТИВНОЇ ПОТУЖНОСТІ В ДАЛЬНІЙ ЕЛЕКТРОПЕРЕДАЧІ ЗМІННОГО СТРУМУ

The components of active power losses in long-distance AC power transmission are investigated. It is shown that in the modes of low and medium loads the main share of losses are corona losses. The imperfection of the current method of determining the corona power losses, which are climatic in nature, determines the method of separating these losses from the total after calculating the load power losses. A four-component formula for determining the load losses of active power is obtained. It is shown that to clarify the calculation model it is necessary to take into account the actual temperature of the wire, taking into account changes in weather conditions along the route of the line. The results of calculation of components of active power losses in the 750 kV overhead transmission line "Zakhidnoukrainska-Vinnytska" during the day of September 13, 2021 are given. References 9, figures 4, tables 3.

STUDY OF THE ELECTROMAGNETIC IMPACT OF THE OVERHEAD TRANSMISSION LINES OF 330 KV ON ECOLOGICAL SYSTEMS

The analysis of factors and approaches to the conditioning of the electromagnetic impact of 330 kV overhead transmission lines on ecological systems has been carried out. The analysis performed enabled to reveal that the world experience, recording the introduction of the transmission lines of the carrying capacity and reduced environmental impact, including the compact and controlled self-compensating lines, is expedient to take into consideration in the process of the object design, as compared with the transmission line of the conventional construction, operated in Ukraine. The technique of electromagnetic field of the 330 kV overhead transmission lines calculation is improved for the ecological systems and to clarify the width of the sanitary protection zone. Unlike other technique, the given one takes into account the line clearance and the sag of, also this technique is universal as it enables to calculate and analyze the variation of the electromagnetic field of the overhead transmission lines of different construction not only on the line route, but also at a distance from it.

Study about numerical relay 7SA612, the basic protection of 220 kV overhead transmission line

In this work we analyzed the numerical relay 7SA612, which represents the basic protection of 220 kV overhead transmission lines starting from the Mintia electric station. The main function of 7SA612 relay is the distance protection; in addition, this relay offers a multitude of protection functions. We used the computer-controlled Omicron CMC 356 set for testing the 7SA612 relay at its mounting location. Test Universe, the software of CMC 356, allowed the simulation of all possible overhead transmission lines faults, in order to test the protection functions of 7SA612 relay. 7SA612 relay clears fast and selectively the faults on the analyzed 220 kV overhead transmission line. The tests showed that 7SA612 relay incorporates all the necessary functions for the protection of 220 kV overhead transmission lines, both in the case of single-phase and poly-phase faults.

БЕЗПЕЧНЕ ВИМКНЕННЯ ЕЛЕГАЗОВИХ ВИМИКАЧІВ У ПОВІТРЯНИХ ЛІНІЯХ ЕЛЕКТРОПЕРЕСИЛАННЯ

The paper analyses the transient currents during the energisation of a 750 kV overhead transmission line (OTL). The safety of OTL state after symmetrical and asymmetrical closing of the circuit breakers and technical feasibility of SF6 circuit breakers opening with time delay after their closing is substantiated. The necessity of transient processes simulation for analysing the characteristics of periodic and direct components of currents is shown. A method for determining of SF6 circuit breaker opening time delay for a set of the states that may arise after the energisation of OTL is developed. References 13, tables 2, figures 5.