1,721,037 research outputs found
Corona effect influence on the lightning performance of overhead distribution lines
No full textOverhead distribution lines can be seriously damaged from lightning events because both direct and indirect events can cause flashovers along the line. The lightning performance of such power lines is usually computed neglecting the effect of corona discharge along the conductors: in particular, the corona discharge determined by the indirect lightning event is taken into account only by few researchers because it can have meaningful impacts only in few cases. However, when we deal with overhead distribution lines with high Critical Flashover value (CFO) and small diameters, the corona discharge caused by indirect events has to be taken into account. This paper shows the effects of corona discharge in the lightning performance computation of overhead distribution lines. The analysis will involve different configurations in terms of line diameter and air conditions, focusing on the negative effect of corona discharge in the number of dangerous events that determine line flashovers
An Overview on Reversible Sea Return Electrodes for HVDC Links
No full textHVDC electrodes are usually implemented in HVDC links to avoid the installation of a metallic return. Submarine cables, especially those dealing with lengths of thousands of kilometers, are expensive, and high costs of laying are normally expected. Due to the high number of reversible HVDC links, the marine electrodes must be able to withstand both anodic and cathodic operations, which leads to careful considerations in terms of the material to be used. This paper shows the state of the art of the currently installed reversible sea return electrodes, focusing on the type of installation (sea, shore or pond electrodes) and on the material used, from the first plant installed in 1954 up to the more recent ones established during the XXI century. All reported data derive from publicly available sources. Moreover, since nowadays environmental issues are among the most important topics, for each material and for each type of installation, a guideline on the possible interferences caused by marine electrodes with the surrounding environment is proposed
A review on the return stroke engineering models attenuation function: Proposed expressions, validation and identification methods
No full textOne of the most important and studied topics in lightning research is the development of suitable models for the return stroke current and electromagnetic fields. In particular, when dealing with the so-called engineering models, the definition of a function that expresses the attenuation of the current while flowing in the discharge channel (from now on, the attenuation function) is of crucial importance for a reliable computation of the lightning discharge electromagnetic fields and the resulting over voltages induced in a power distribution electric system. The paper contributes to such topic in two ways: first of all, a review of all the well-known engineering models is presented, highlighting the definition of each attenuation function and comparing the models in terms of the resulting overvoltage induced on a typical distribution line. Secondly, an innovative idea based on the possibility of reconstructing the attenuation function starting from the measured electromagnetic fields is presented. The state of the art in this research line is outlined and the issues that are still open are presented. In particular the possibility of adopting the so-called regularization techniques to solve ill posed inverse problems to evaluate the current starting from electromagnetic fields is addressed analysing the available results and highlighting that, to the best of the authors knowledge, these techniques have never been applied with experimental data
Simulation and design of a large thermal storage system: Real data analysis of a smart polygeneration micro grid system
No full textThe Smart Polygeneration Microgrid (SPM) at the Savona Campus of the University of Genoa consists of several renewable and traditional electrical and thermal generating units integrated with electric batteries; buildings and facilities are connected by an electrical grid and a district heating network. Thermal and electrical power flows are managed by a proper Energy Management System (EMS) which includes models for all the SPM components ensuring operational costs minimization in compliance with networks constraints. The present study focuses on the integration of a thermal energy storage (TS) system in the SPM: to this aim, a new thermal storage model based on a stepped two-zone approach has been built inside the dynamic EMS solver. The TS is conceived for recovering additional heat from two 65kWel cogenerative gas turbines (CGT), thus minimizing the operation time of the backup gas heaters (GH): the analysis is aimed at inferring the best TS size in terms of different key parameters, expressed through properly defined economic and energy criteria, including overall energy consumption, reduced greenhouse emissions, minimum payback period. The model is applied to energy demand data (heat and electricity) as measured at 15 min time steps along 2 years. The present dynamic analysis shows that an optimized size TS based on sensible heat can increase the CGT operation hours up to 34% yearly and reduce the equivalent CO2 emissions by 4%
Lightning Location and Peak Current Estimation From Lightning-Induced Voltages on Transmission Lines With a Machine Learning Approach
Full text linkIn this article, a machine-learning-based model for the regression of cloud-to-ground lightning location and peak current from time-domain waveforms of lightning-induced voltage measurements on overhead transmission lines is presented. A principal component analysis (PCA) procedure is applied for extracting significant features and decreasing the dimension of the input vector. Then, a shallow neural network is trained with the results of the PCA. The obtained results show that the proposed approach can be the base for a tool able to regress lighting location with an accuracy comparable to or even better than traditional methods [i.e., lightning location system (LLS)] and provide a peak current estimate more accurate than LLS and more actual and widespread than direct tower measurements (which are limited to a reduced number of recorded events in some specific regions). Such a tool would also have significant advantages in terms of costs, since it would not require a dedicated instrumentation
Relating transmission line overvoltages and lightning location: a machine learning–based procedure
No full textPurposeThis study aims to investigate the use of machine learning-based algorithms in the field of lightning stroke localization. This work is an important step ahead with respect to the research recently started by the authors, i.e. the possibility of locating a lightning discharge from the voltage induced on overhead transmission lines; more in detail it seeks new insights into the inclusion of both first and subsequent return strokes of negative cloud-to-ground flashes.Design/methodology/approachThis study uses a quantitative approach, using supervised learning techniques for a regression problem (data preprocessing, model selection, training, testing, validation or algorithm optimization). Data are collected from a dedicated lightning-induced overvoltage simulator and analyzed using a specific machine learning-based procedure developed and programmed by the authors.FindingsThe results reveal significant improvements in localization accuracy for both first and subsequent strokes, with respect previous works, indicating that the novel approach is promising for future investigation with more complex power system configurations and the use of experimental data. These findings provide evidence that dedicated models for each type of stroke yield better performance, offering significant implications for the integration of machine learning-based lightning location systems into the existing power infrastructure.Originality/valueThe proposed method is, to the best of the authors' knowledge, entirely new and constitute an innovation with respect to the present literature, both of the same authors and of other research groups. In particular, a new preprocessing procedure of the voltage data is proposed, and the performances of different neural networks are evaluated, both for the first and the subsequent stroke. The application to both first and subsequent stroke is an innovation itself because it has not been proposed before
The Lightning Power Electromagnetic Simulator for Transient Overvoltages (LIGHT-PESTO) Code: A User-Friendly Interface With the MATLAB-Simulink Environment
No full textThe protection of power lines from lightning transients is a crucial issue that has involved the efforts of many researchers around the world. The need of relying on a precise method for the computation of the overvoltages waves travelling on the transmission lines is fundamental when the possible occurrence of flashovers has to be evaluated. The overvoltages behavior is directly related to the complexity of the power systems: as a consequence, a tool able to take into account this factor has a strong importance in the research framework. This letter presents the Lightning Power Electromagnetic Simulator for Transient Overvoltages (LIGHT-PESTO) code, which is based on an interface of a previous developed algorithm for the computation of lightning transients on a power line with the MATLAB-Simulink environment. The proposed interface allows the user to set in an easy and intuitive way the main parameters related to the lightning channel, to the overhead transmission lines, to the ground and to the surrounding power system
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