Lightning Modeling and Its Effects on Electric Infrastructures

When it comes to dealing with high voltages or issues of high electric currents, infrastructure security and people’s safety are of paramount importance. These kinds of phenomena have dangerous consequences, therefore studies concerning the effects of lightning are crucial. The normal operation of transmission and distribution systems is greatly affected by lightning, which is one of the major causes of power interruptions: direct or nearby indirect strikes can cause flashovers in overhead transmission and distribution lines, resulting in over voltages on the line conductors. Contributions to this Special Issue have mainly focused on modelling lightning activity, investigating physical causes, and discussing and testing mathematical models for the electromagnetic fields associated with lighting phenomena. In this framework, two main topics have emerged: 1) the interaction between lightning phenomena and electrical infrastructures, such as wind turbines and overhead lines; and 2) the computation of lightning electromagnetic fields in the case of particular configuration, considering a negatively charged artificial thunderstorm or considering a complex terrain with arbitrary topograph

Outdoor Insulation and Gas Insulated Switchgears

This book focuses on theoretical and practical developments in the performance of high-voltage transmission line against atmospheric pollution and icing. Modifications using suitable fillers are also pinpointed to improve silicone rubber insulation materials. Very fast transient overvoltage (VFTO) mitigation techniques, along with some suggestions for reliable partial discharge measurements under DC voltage stresses inside gas-insulated switchgears, are addressed. The application of an inductor-based filter for the protective performance of surge arresters against indirect lightning strikes is also discussed

Traumatic effects of lightning strike on human bone morphology and ultrastructure

A Dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science FACULTY OF HEALTH SCIENCES UNIVERSITY OF THE WITWATERSRAND, JOHANNESBURG 2016South Africa reports lightning fatality rates as high as 8.8 per million annually. Traditionally, forensic lightning fatality identification consists of soft tissue traumatic pattern recognition. This does not allow for manner of death identification in cases of full skeletonization. This study has expanded upon our earlier research, which identified characteristic patterns of lightning disruption in non-human bone. We thus explored the effects of induced lightning high voltage current on human cadaveric material in order to recognise electrically induced trauma. The objectives comprised analysis of microstructural damage through conventional thin-section histology, micro-focus computed tomography and histomorphometry. Experimentation was undertaken on bone blocks extracted from human lower limbs obtained from cadaveric specimens. An experimental system for simulated lightning induction to bone was developed and investigations were carried out on twenty-two bone block specimens. Micro-focus computed tomography was undertaken prior and after experimental treatment; while three blocks were used unmodified as control samples. Thin sections were obtained following post-trauma imaging. Measurements and photomicrographs of the alteration patterns were taken, while micro-focus computed tomography data were reconstructed and visualised as 2D orthoslices and 3D rendered volumes. Results indicated a poor efficiency of micro-focus computed tomography to resolve traumatic features in cortical bone. However, conventional histological methods demonstrated cortical bone trauma patterns well, allowing easy identification. Statistical analyses demonstrated relationships between current intensity and extent as well as typology of damage observed. The relationships identified suggested a dual mechanism of bone trauma, consisting of a combination of both electrically and thermally induced alterations. This study has thus allowed a primary overview and analysis of lightning trauma to human skeletal tissues.MT201

A feasibility study on the three-dimensional reconstruction of high voltage and lightning descharge channels using digital images

The work presented extends and contributes to research in the visualisation of discharge channels with an expectation to extend to lightning channels. Although previous work in this area has produced three-dimensional (3D) information of discharge channels, there has not been a method to visualise the channel and the characteristics of its shape in a 3D environment. In the research presented, photographed discharge channels are reconstructed in a virtual interactive 3D envi- ronment. It is found that single-channelled discharges produce models that correctly follow the inferred channel paths from the photograph datasets. Single-channelled discharges have also been veri ed in the controlled laboratory environment, providing con - dence in the two-image reconstruction algorithm. The algorithm is shown to fail for an angular separation of cameras less than 15 , which produces thicker channel segments. It is further shown that branched discharge channels can produce models that correctly follow the channel paths. If images are not accurately normalised for lens correction and slight camera tilts, missing segments and duplication of reconstructed branches are evident in the models. Furthermore, it is shown that the algorithm also fails for image perspectives with angular separations less than 15 , additional redundant branches are produced in addition to thicker channel segments

Effect of water on electrical properties of Refined, Bleached, and Deodorized Palm Oil (RBDPO) as electrical insulating material

This paper describes the properties of refined, bleached, deodorized palm oil (RBDPO) as having the potential to be used as insulating liquid. There are several important properties such as electrical breakdown, dielectric dissipation factor, specific gravity, flash point, viscosity and pour point of RBDPO that was measured and compared to commercial mineral oil which is largely in current use as insulating liquid in power transformers. Experimental results of the electrical properties revealed that the average breakdown voltage of the RBDPO sample, without the addition of water at room temperature, is 13.368 kV. The result also revealed that due to effect of water, the breakdown voltage is lower than that of commercial mineral oil (Hyrax). However, the flash point and the pour point of RBDPO is very high compared to mineral oil thus giving it advantageous possibility to be used safely as insulating liquid. The results showed that RBDPO is greatly influenced by water, causing the breakdown voltage to decrease and the dissipation factor to increase; this is attributable to the high amounts of dissolved water

Effect of substrate bias voltage on structural and tribological properties of W-Ti-C-N thin films produced by combinational HiPIMS and DCMS co-sputtering

Protective multi-component thin films at the surface of cutting tools have been significantly developed to reduce wear and friction. The present work investigates the effect of substrate bias voltage on the structural-tribological relations of W-Ti-C-N thin films produced by HiPIMS and DCMS co-sputtering. Chemical analysis of the coatings is obtained and composite phase structure is revealed. Morphology of the coatings illustrates that defectless surfaces may be achieved. Topographical parameters are investigated by employing graphical software. Indentation, scratch and pin-on-disk tests (pin is AISI 52100 steel) are applied to study mechanical behaviors of the films. To produce a wear-resistant film, a median bias voltage ( 60 V) and as a result, optimum content of tungsten concentration (19.2 at. %), grain size (42.8 nm) and average peak interval (188 nm) is required. Finally, a model based on the representative volume element is developed to show crack propagation and delamination.info:eu-repo/semantics/publishedVersio

High Voltage Insulating Materials-Current State and Prospects

Studies on new solutions in the field of high-voltage insulating materials are presented in this book. Most of these works concern liquid insulation, especially biodegradable ester fluids; however, in a few cases, gaseous and solid insulation are also considered. Both fundamental research as well as research related to industrial applications are described. In addition, experimental techniques aimed at possibly finding new ways of analysing the experimental data are proposed to test dielectrics

Modern Applications of Electrostatics and Dielectrics

Electrostatics and dielectric materials have important applications in modern society. As such, they require improved characteristics. More and more equipment needs to operate at high frequency, high voltage, high temperature, and other harsh conditions. This book presents an overview of modern applications of electrostatics and dielectrics as well as research progress in the field