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An overview of recent results of high-speed video observations at the Lightning Observatory in Gainesville (LOG), Florida, is given. The emphasis is placed on the lightning attachment process and interaction of lightning with tall grounded objects.
Risk estimates for lightning faults make use of log-normal distributions for lightning characteristics such as peak current. Simplifications for highly correlated parameters, notably peak current and rate of current rise, justify use of equivalent front time of 2 µs in backflashover calculations for first negative return strokes. The transmission line backflashover rate is also affected by uncorrelated...
The paper is motivated by the results obtained in a joint project between the Brazilian electric distribution utility AES Sul, the Federal University of Itajubá and the University of Bologna. It deals with some aspects relevant to the assessment of the lightning performance of medium voltage (MV) overhead power distribution lines and of MV distribution feeders mainly composed by overhead lines. In...
We report simultaneous measurements of vertical electric fields and currents associated with positive flashes to the Säntis tower. The fields were measured at a distance of 14.7 km from the tower. All the data correspond to type-2 positive flashes characterized by currents with relatively slow rising portion on which oscillatory pulse trains, inferred to be due to an upward negative stepped leader,...
This work aimed to investigate which pulses (M-components and/or subsequent return stroke) of the upward lightning are detected by BrasilDAT lightning location network. It was found that, these pulses are similar to downward lightning pulses and therefore, they were well detected by the network. This report is based on a set of 29 upward lightning and 16 downward lightning whose strike points are...
Two methods for modeling the electromagnetic fields near a lightning channel are considered. These methods can be used in evaluating the effect of a lightning electromagnetic pulse (LEMP) on a distribution line. The first method for evaluating LEMP fields in the time domain uses a Heidler function approximation for the channel base current in the classic Finite Antenna method. This approximation has...
This paper analyses the lightning induced voltages in large loops, considering the propagation of the scattered voltages along the loop. The loop is modeled as a transmission line having two possible configurations: two wires above ground and one wire above ground. The inducing electric field components are introduced gradually, in order to identify the effect of each one of them. It is shown that...
Among the various factors that influence the lightning electromagnetic fields, the presence of obstacles such as buildings has deserved some few studies. The paper presents the results related to the influence of a group of buildings on the vertical electric field, by a 3D FDTD code developed for a more complete study. Two rows of concrete buildings were considered, with different heights, areas and...
Direct and indirect lightning strokes can cause severe overvoltages in distribution networks and, consequently, failures and power outages, due to insulation problems and equipment damages along the network. In order to assist the analysis of lightning effects in power quality indices, we present in this paper, a detailed analysis of the local electric field, combined with the information from Lightning...
The major cause of lightning disaster is the Lightning Electromagnetic Pulse (LEMP). Disaster risk assessment services have been widely used in lightning protection centers of many cities in China for years. At present, electromagnetic environment assessment services are being used more and more at many lightning protection centers in China, with various methods. Most of them adopt an expensive commercial...
The ability to evaluate the possibility of a lightning discharge is a important resource in making safety-related decisions, and enables the reduction of losses due to shutdowns in the energy sector, as well as other damages. The atmospheric electric field sensors are used to measure the magnitude of the electric field in a region between the earth and a storm cloud, and estimate how much the value...
Current distribution within a new gradient observation tower has been calculated by finite-difference time-domain (FDTD) method. The current through Metallic stay cables which are designed to reinforce tower body has been take into account. It is found that a large portion of lightning current would be absorbed by stay cables. Ground level electrical field is also given by the calculation. In addition,...
This paper presents a low-cost system to detect and store lightning waveforms in VLF (3–30khz) or ELF (3–3000Hz) frequencies. The name of the system is: Lightning Detection and Waveforms Storage System (LDWSS). The system consists of a whip antenna with a fully-programmable pre-amplifier and filtering circuit and a microcontroller to process the signal and send the data to a computer where it will...
In this paper the electrical and magnetic field interference in inhabited rights-of-way produced by a 115 kV double circuit transmission line is analyzed The software used in this investigation was COMSOL Multiphysics®. Results were validated with electric and magnetic field site measurements.
The paper presents an alternative to the traditional method of lightning protection of 35 kV overhead lines based on shield-type multi-chamber arresters. The main stages of the design of arrester, and also shows the test results confirming compliance with required characteristics.
In order to evaluate if metal oxide surge arrester present any partial discharge (PD) in case of internal moisture and how applicable it is as a condition monitoring diagnostic method, 8 distribution class (Ucov = 20 kV) metal oxide surge arresters (6 silicone housed and 2 Ethylen-Vinylacetate (EVA) housed) from four different manufacturers (A, B, C and D) were submitted to an immersion test for 19...
There are various kinds of surges in LV system superposing the AC operating voltage. This document presents the test on MOV type SPDs to discover the possible reasons for fire under operation that are observed in field. The tests are including the AC test, surge test, surge on AC voltage and multiple surges. The test results lead to the solutions on how to deal with the safety problem.
In this paper the behavior of an earthing system when a 100 kA, 10/350 lightning current is applied to a grounded mast is investigated. The numerical calculations were performed using the transient solver of CST Microwave Studio, a finite technique based computer program. CST was used to calculate induced step and touch voltages in the mast under grounded with and without a protecting fence or enclosure...
The main challenge of this article is to show a feasible solution for measuring earth resistance at short distances, considering that in practical terms, such is the condition found in the great majority of urban substations. A field test with 4 grounding meshes with different geometric configurations was implemented and used in order to perform a great number of measurement tests. Based on all the...
This paper presents a preliminary study on the effect of dispersive ground parameters on surges transferred from medium-voltage to low-voltage distribution lines located in rural areas. In this study, a direct lightning strike is assumed at different points of a distribution line terminated at a 10 kVA 7.967 kV/240–120 V single-phase transformer with center-tapped secondary. The distribution line...
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