Overhead Distribution Networks Research Articles

Monitoring of insulator pollution discharge in overhead distribution network based on acoustic emission technology

Abstract During the continuous operation of the distribution network, dirt often accumulates on the surface of insulators. Once encountering a humid climate environment, it may cause accidental discharge, leading to the occurrence of flashover pollution accidents. In order to effectively monitor this issue, this study adopted a monitoring method based on acoustic emission technology. This article introduces the discharge process and acoustic emission phenomenon of insulators in overhead distribution networks under pollution conditions. By using emission signal detection devices, acoustic signals generated during insulator discharge are captured. And the wavelet denoising algorithm was used to process its signal, based on which the discharge characteristics of insulator pollution in the overhead distribution network were extracted. The emission amount of insulator pollution in the overhead distribution network was determined according to the set threshold, achieving monitoring of pollution emissions. The results indicate that the proposed method can accurately monitor the discharge of insulators in overhead distribution networks, provide scientific basis for timely maintenance measures, and improve the operational safety and reliability of distribution networks.

Detection of Underground Utility Pole Base for Distribution Transmission Network Based on Transient Electromagnetic Method

In the construction of overhead distribution network lines, ensuring the stability and construction quality of utility pole foundations is crucial. Traditionally, this process may involve excavation and direct inspection, which is not only time-consuming but may also cause environmental damage. The non-destructive detection scheme proposed in this paper, based on the transient electromagnetic method (TEM), offers an efficient and non-intrusive method for detecting the burial conditions of utility pole bases, pulls, and chucks. The transient electromagnetic method is a geophysical exploration technique that uses the principle of electromagnetic induction to detect the distribution of underground materials. When detecting utility pole bases, this method analyzes the electromagnetic response generated by underground metallic structures to obtain information. However, traditional TEM has a blind zone problem in shallow metal detection, which limits its application in utility pole base inspection. To address this issue, the scheme proposed in this paper introduces a decoupling coil to eliminate interference caused by the primary magnetic field. This decoupling technology significantly improves the detection discrimination, allowing for a more accurate determination of the burial depth and condition of bases, pulls, and chucks. Finite element numerical analysis using COMSOL 5.4 is adopted to examine the underground magnetic field distribution and optimize coil parameters. This analysis helps to understand the interaction between the electromagnetic field and underground structures, guiding the design of coils and the development of detection strategies. The prototype experimental platform built further validates the effectiveness of the scheme. Experimental results include measured data of magnetic field variations, assessments of detection depth and resolution. These experimental results are crucial for verifying the practical application potential of the non-destructive detection scheme.

High Impedance Fault Models for Overhead Distribution Networks: A Review and Comparison with MV Lab Experiments

Detecting and locating high impedance faults (HIF) in overhead distribution networks (ODN) remains one of the biggest challenges for manufacturers and researchers due to the complexity of this phenomenon, where the electrical current magnitude is similar to that of the loads. To simulate HIF, the selection of the HIF model is important, because it has to correctly reproduce the characteristics of this phenomenon, so that it does not negatively influence the simulations results. Therefore, HIF models play a fundamental role in proposing solutions and validating the effectiveness of the proposed methods to detect and localize HIF in ODN. This paper presents a systematic review of HIF models. It is intended to facilitate the selection of the HIF model to be considered. The models are validated based on experimental data from medium voltage (MV) laboratories, specifically, recorded waveforms from two HIF tests conducted in an MV lab were analyzed and compared with three established HIF models. The efficacy of these models was assessed against MV lab test data to ensure a precise representation of both transient and steady-state conditions for fault conductance and current waveforms. The findings show that the two nonlinear resistor models better approximate the waveforms obtained in the experimental tests performed in this study.

Improve operator safety & protect wildlife in overhead distribution networks

Improve operator safety & protect wildlife in overhead distribution networks

Construction Schedule of Medium Voltage Overhead Distribution Network Optimization Based on Neural Network Algorithm

INTRODUCTION: The medium voltage overhead distribution network is a complex planning problem, and monitoring the construction progress of the medium voltage overhead distribution network is an important aspect of the planning problem. Regarding the structure of the medium voltage overhead distribution network, it is one of the important components in China's distribution network system. If the construction progress of the medium voltage overhead distribution network is optimized, it will affect the normal operation of the entire power grid system in a certain region. Optimizing the construction progress of medium voltage overhead distribution networks using modern development related technologies or algorithms is one of the practical research topics. OBJECTIVES: To better predict various issues that may arise during the construction progress of the distribution network. Complex geographical conditions lead to construction difficulties, and lack of technology leads to frequent stoppages of construction, further leading to frequent power outages in various regions. In terms of the overall power supply system, the reliability of power supply is not high. METHODS: By comparing the BP neural network algorithm with the CNN network algorithm, the actual operation effect is evaluated by experts. RESULTS: This article predicts the implementation progress of the medium voltage overhead distribution network, and the results show that the accuracy of the BP model for predicting the construction progress of the medium voltage overhead distribution network can reach 88%; The accuracy of the CNN medium voltage overhead distribution network construction progress prediction model reaches 77%. CONCLUSION: The use of neural network algorithms to optimize the construction schedule of medium voltage overhead distribution networks has been evaluated by experts in practical applications, and the medium voltage overhead distribution network in power supply systems has potential application value.

Lightning Protection With a Differentiated Configuration of Arresters in a Distribution Network

When concerning the installation and operation costs, it is always desirable to protect an overhead distribution network with a limited quantity of surge arresters (SAs). This paper presents a novel procedure for designing differentiated protection against lightning, by identifying appropriate positions for those SAs on the overhead line. Rather than the traditional flashover rate of a whole line, indices in terms of flashover numbers at individual poles and associated with possible stroke locations are introduced in this paper. Based on these flashover indices, a differentiated configuration of SAs can be identified using a selection strategy. After several rounds of selection, a differentiated SA protection scheme can be obtained, given by a pre-set quantity of SAs. In this procedure, a simplified probability-based approach is proposed to determine the flashover indices. By comparing the traditional Monte Carlo method, this approach can achieve a 10-fold increase in computational efficiency with reasonable accuracy. Two different selection strategies are introduced in this paper. Compared with the selection strategy using the flashover indices at individual poles, the selection strategy based on a group of poles is recommended because it yields a configuration with better lightning performance with the same quantity of SAs. This design procedure is applied to practical distribution networks with a shield wire and nearby structures. The influence of grounding impedance, a shield wire, and nearby structures is addressed. Finally, a generalized step-by-step procedure is provided to assist in a differentiated SA protection design.

Application of Digital Twin in Medium-Voltage Overhead Distribution Network Inspection

The paper is devoted to the digital transformation of the core engineering maintenance processes involved in medium-voltage overhead distribution network infrastructure inspection. The study presents an analysis of digital twin utilization for inspection of the infrastructure of medium-voltage overhead distribution networks. At present, the infrastructure monitoring process is still manual, and its automatization is a challenging task due to the large distances between and small dimensions of the elements involved. The proposed digital twin is employed for 3D infrastructure modeling and complex analysis based on photogrammetry and aerial scanning data processing methods. The paper describes practical use cases for these data-driven methods for specific infrastructure management processes, e.g., scheduled inspection processes, including geometrical parameter measurements and visual infrastructure element defect identification, unplanned inspection processes (state of emergency, post-storm, etc.), and vegetation management processes. The proposed method allows operations to be performed remotely without physical presence in the field. At the same time, data-driven solutions provide objective results and potential automation via machine learning algorithms, which are more profitable economically. As the proposed method allows processes to be performed remotely, these data-driven solutions offer cost-effective results for automation. The digital twin concept is applied to the Latvian medium-voltage overhead distribution network with the support of the Latvian distribution system operator “Sadales tīkls” JSC.

High-impedance fault detection on downed conductor in overhead distribution networks

High impedance faults (HIF) may occur in the medium voltage distribution systems and constitute a danger to human beings. Many cases of HIF are caused due to downed power cables in the distribution network. These cables in contact with the ground generate a great risk to the population, animals and fire risk. In this paper, a methodology for detecting HIF, generated by cable breakage, is presented. The algorithm is based on the analysis of the harmonic and symmetrical components of the current. The method aims to gain reliability in HIF detection, where the detection of conductor breakage incorporated into the method allows a better distinction of HIF from other events. A distribution network based on a Brazilian real feeder was implemented, as well as two well know HIF models. The method is validated using real-time digital simulations and hardware implementation, or HIL (hardware-in-the-loop) concept with OPAL-RT real-time simulator. A comparison with other methods is also performed in order to evaluate the performance of the method. The results show that the proposed methodology has presented a better performance under different types of HIF, models of HIF, and achieved a general accuracy of 90% and security of 100% for the tests performed.

Accelerated Protection (AP) scheme in overhead distribution networks

It is a new philosophy of protection in distribution networks, whose objective is to reduce, in an unconventional way, the sum of the operating times (exposure) of the protection equipment (reclosers and circuit breakers) on the short-circuit currents, while throughout the automatic reclosing cycle, maintaining the coordination of the protection system. From the protection point of view, this philosophy can be applied mainly in feeders that contain a large number of protection devices in series, which results in long operating times and exposure to fault currents, especially in devices further upstream in the feeders, with using conventional protection philosophies. Pilots of this new philosophy were applied, which presented satisfactory and even surprising results (in cases of broken cables), thus, resulting in a roll-out process of this philosophy in about 400 other devices protection in the utility grid, presenting good scalability due to possibility of its application in all models of IEDs of reclosers and circuit breakers of the utility that are found on the market. This scheme was elaborated and managed through the project called Urban Futurability, which consists of an R&D project performed at Enel-SP.

Location and Extraction of Telegraph Poles from Image Matching-Based Point Clouds

The monitoring of telegraph poles as essential features supporting overhead distribution network lines is the primary subject of this work. This paper proposes a method for locating and extracting telegraph poles from an image matching-based point cloud. Firstly, the point cloud of the poles is extracted using the planar grid segmentation clustering algorithm and the connected component analysis algorithm of the region grows according to the isolated features of the poles perpendicular to the ground. Secondly, the candidate telegraph poles are located based on the suspension point of the buffer, considering that the top of the pole is connected to the power suspension line. Thirdly, the horizontal projection method of the backbone area is utilized to eliminate the interference of vegetation in the buffer area. Finally, the point cloud of the telegraph pole is extracted through the density-based spatial clustering of applications with noise (DBSCAN) algorithm. The experimental results demonstrate that the average values of Recall, Precision, and F1-score in telegraph pole detection can reach 91.09%, 90.82%, and 90.90%, respectively. The average RMSE value of location deviation is 0.51m. The average value of the F1-score in the telegraph pole extraction is 91.83%, and the average extraction time of a single pole is 0.27s. Accordingly, this method has strong adaptability to areas with lush vegetation and can automatically locate and extract the telegraph pole point cloud with high accuracy, and it can still achieve very high accuracy even under the holes in the data.

High-Impedance Fault Detection on Downed Conductor in Overhead Distribution Networks

High-Impedance Fault Detection on Downed Conductor in Overhead Distribution Networks

Impact of climate change on network components: Root Cause Analysis of overhead distribution network failures due to heavy Snowfall- a Case Study Gilan, Iran, Feb. 2020

Climate change has inflicted many damages to our planet. Among these damages, harsh weather conditions such as storms, heavy snowfalls are quite catastrophic. They have sometimes become unpredictable as well as posing great damages to everything such as overhead lines. In the absence of preventive actions, our network infrastructure could become extremely vulnerable. Snowfall phenomenon is a High Impact Low Probability (HILP) contingency, which causes moderate risk. A heavy snowfall which occurred in Rasht, Gilan province, Iran, February 2020, was investigated by a technical committee in Tavanir Company. It was a very devastating accident; many outages (about 90,000 consumers) were announced in 194 villages of this province. The main power outage was due to failure of equipment and overhead line's inappropriate mechanical design strategies. In this paper, main causes of network weak points, which resulted in this huge destruction and blackout, are carefully determined. Effective solutions for minimizing weak points in two parts of electrical networks (LV, MV) are developed. Then, applying Root Cause Analysis method (RCA) and Analytic Hierarchy Process (AHP) model, a pattern is presented that increases resiliency of the network against heavy snow.

Selection of parameters of overhead lines models when calculating transient processes during earth faults in 6–10 kV networks

Single phase-to-ground faults are the most common type of faults in 6–10 kV overhead distribution networks. Arc intermittent single phase-to-ground fault (PSP) are the most dangerous for the network and the damaged element. They are followed by intense transient processes and, as a result, dangerous overvoltage rate and significant transient current surges at the point of insulation damage. PSP transients also have a significant effect on the selectivity and operation stability of protection devices against this type of damage. Therefore, the development of the methods and means to improve the operation efficiency of 6–10 kV overhead networks in case of PSP and technical improvement of protection devices in many cases is due to the need to calculate the transient processes that occur during insulation breakdowns of the network phase to earth. For the systems under consideration, the reliability of transient processes calculations in case of PSP is determined mainly by the accuracy of estimation of the parameters of 6–10 kV overhead lines, first of all, of inductance, which generally depends on the frequency of the transient current components. In the scientific papers devoted to the study of transient processes in case of PSP in medium voltage electrical networks, including 6–10 kV overhead networks, constant (frequency independent) values of inductance are used as a rule in the equivalent circuits and in the models of transmission lines. An urgent task is to estimate errors caused by the application of this approach to determine the parameters of 6–10 kV overhead lines during the calculations and modeling of transient processes during PSP, and cases of its application. Advanced methods of modeling of electric power systems and their elements have been applied with the use of COMSOL Multiphysics and PSCAD software to obtain the frequency dependences of the inductances of a 6–10 kV three-phase overhead line and study of their influence on the calculation accuracy of transient currents and voltages in case of PSP. The parameters of 6–10 kV overhead line models developed in the indicated software packages at a frequency of 50 Hz are set in accordance with the reference data. The authors obtain the errors estimation to determine the parameters of transient currents and voltages during PSP in 6–10 kV overhead networks when using transmission line models. The frequency dependences of inductance, which are up to 40–50 % in amplitude are not considered. The results show that application of frequency-independent models is permissible only in the cases when parameters of the calculated equivalent circuit of the network and position of PSP point remain practically constant, when solving problems that require high accuracy to determine the parameters of transient currents and voltages, for example, to determine remotely the location of a ground fault, it is necessary to use frequency-dependent models of 6–10 kV overhead lines. Introduction of the developed recommendations to determine 6–10 kV three-phase overhead lines parameters allow us to increase the reliability of calculations and to avoid raw errors when solving the problems which are related to the study of transient processes in case of earth faults in the networks of the given voltage class.

Improving the functioning efficiency of 6-10 kV electrical networks with isolated neutral in conditions of single-phase ground faults

The main objectives of this publication are: 1) to attract the attention of energy specialists to the problems of reliability and electrical safety of 6-10 kV overhead electrical networks with isolated neutral, operating in conditions of single-phase insulation damage; 2) substantiation of the feasibility of introducing a fundamentally new way to improve the efficiency of 6-10 kV distribution networks, based on the resonanceless limitation of the single-phase ground fault current arising from the breakdown of the insulator and the use of its own infrastructure of the electrical network for remote identification of the place of its occurrence. The expediency of including a nonlinear surge suppressor between the traverse and the grounding outlet of the reinforced concrete support is confirmed by the positive results of experimental studies carried out on the basis of high-voltage testing laboratories of IDGC of Center PJSC - Orelenergo and EnerGarant LLC. The use of deductive analysis allowed the authors to select a reliable and affordable electrical insulating material installed between the support and the traverse, as well as to formulate the main requirements for it, including taking into account weather and climatic factors. The analysis of various methods of transmitting information about the place of occurrence of the insulator damage made it possible to establish the predominant advantage of a wired communication channel using its own 6-10 kV electric network infrastructure. The authors have developed an original circuitry solution that provides remote identification of the insulator damage location using a thyristor shunting the nonlinear surge suppressor, according to a given switching algorithm, and also provides local identification of the insulator breakdown by means of special signaling devices with volatile power supply. It is expected that the proposed method, with relatively low investment, will significantly reduce the level of accidents and electrical hazards in overhead distribution networks of 6-10 kV, as well as minimize the costs associated with their operation and undersupply of electrical energy.

Design of Range Sensor for Transmission Line Fault Detection in Covered Conductor Overhead Grid

As an important detection means of partial discharges, range sensor is widely used in power system in China. Due to the complex and open environment around covered conductor overhead distribution networks, misjudgement and leakage in long-distance of traditional ultrasonic sensors often occur. Aiming at this problem, an range sensor with high sensitivity and directivity is designed in this paper. In this paper, the theoretical model of the ultrasonic screening can is established by COMSOL simulation software, and the structure of the screening can is designed reasonably by analyzing the concentr-ation and directivity of the sound field of the model. In addition, based on the ultrasonic characteristics generated by partial discharge of overhead insulation wire, the ultrasonic probe with a central frequency of 40kHz was selected, and an amplification and filtering circuit was designed to reasonably improve the signal-to-noise ratio of ultrasonic detection signal. The results of laboratory test and field application show that the sensor can accurately detect and locate the partial discharge of covered conductor overhead distribution networks.

A voltage-based detection method for lightning discharges at distribution networks

Overhead distribution networks, due to its exposed nature, are susceptible to the incidence of Lightning Discharges (LD), especially in rural areas. One way commonly employed by power utilities to detect this phenomenon is by using lightning detection systems based on electromagnetic interference propagation. However, these systems do not normally allow for an accurate conclusion if a lightning strike has occurred in a particular feeder. Therefore this paper presents a methodology for detecting such disturbances by measuring voltages at the substation. The scheme is based on a combination of Park and Wavelet transforms applied to these signals. The paper presents a detailed modeling of the IEEE 34 bus test feeder specific for lightning discharges studies. The results show that with the signature of the LD within the measured signals it is possible to detect the transients associated with. This information can be used as a complement of the traditional meteorological based detection systems.

Methodology for Analysis of Electric Distribution Network Criticality Due to Direct Lightning Discharges

Direct lightning discharges in overhead distribution networks invariably cause serious insulation damage, frequently leading to the electric system’s partial or total shutdown. Installing lightning arresters can be very effective, and it is commonly used to minimize this problem; however, considering that typically, electric distribution grids exhibit a very large number of electrical nodes, the massive use of lightning arresters may not be economically viable. In this way, this article proposes a methodology for allocating lightning arresters that can significantly reduce the number of lightning arresters installed, but at the same time maintaining an adequate protection level for the distribution grid. The proposed methodology, named Direct Discharge Crossing (DDC), analyzes the network criticality based on two main factors, which are the overvoltage magnitudes and the number of flashovers provoked by lightning discharges, and defines a feeder lightning performance function that is used to indicate the recommended location for lightning arresters’ installation. The simulation studies are accomplished using the IEEE 34 bus distribution grid and ATP software to demonstrate the efficacy of the proposed solution, which is confirmed by the results presented.

Impact of covered conductors on Ghana’s distribution network

Electrical power outages experienced in the vegetation areas in Ghana are as a result of bare conductors coming in contact with grounded objects such as trees and tree branches. To curb this problem, the electricity company of Ghana has introduced into its overhead distribution networks the use of CC, covered conductors. These covered conductors unlike the traditional bare wire conductors are able to temporarily withstand phase-to-phase earth voltages. XLPE, Cross-Linked Polyethylene, HDPE, High Density Polyethylene covered conductors together with ABC, Aerial Bundled Conductors are considered. Limitations associated with these covered conductors, greatly relating to cost, reliability, supply quality and safety have been discussed in this paper.

Planeación óptima de redes aéreas de distribución basada en teoría de grafos

Este trabajo presenta un modelo para optimizar los recursos utilizados en la planeación de una red de distribución aérea, la cual permite el despliegue de los transformadores considerando su cobertura y su capacidad. Muestra un modelo de enrutamiento de la red de media tensión basado en minimun Steiner tree para encontrar la mejor ruta en una zona georreferenciada. La planeación se realiza sobre un escenario georreferenciado con datos de la plataforma OpenStreetMap, con el fin de que la localización de los transformadores y la topología de la red sean reales. Los valores obtenidos muestran un punto de partida para que las empresas de distribución eléctrica establezcan planes de trabajo para la expansión y planificación de la red eléctrica de distribución, considerando la variabilidad a la que se presenta la demanda.

Spacer Design for 15 kV Compact Overhead Distribution Networks for Regions with High Environmental Aggressiveness

The aim of this paper is presenting the studies to development of 15 kV spacer design with dimensions and geometry suitable for operation of these in compact overhead distribution lines with high environmental aggression. Computer simulations to evaluate the electric field distribution in different projects of compact overhead distribution networks spacers were made, including conventional models and other with dimensions, geometries, materials and/or product design changes. Additionally, multi stress assays were performed in order to evaluate some of the indications obtained in computer simulations by applying cycles of salt spray under pressure and electric current.