1,721,040 research outputs found
Grounding System in Marinas: The Microsystem Approach
No full textThe microsystem design approach of electric systems has the purpose to improve their safety, maintenance, operation, and reliability. The microsystem design approach can be applied to the case of marinas, where pleasure craft may be moored. Marinas require a structured architecture for the shore electrical power distribution system, which supplies power to distributed loads. In addition, the design must provide for solutions to electrical hazards, as possible stray currents circulating through the earth and the water. The island-grounding system, which utilizes separation transformers grounded at the midpoint of their secondary sides, allows to supply loads divided into "islands" as independent electrical areas. This distribution system is an effective way to protect persons from shock hazards in installations with contained demand load and to greatly limit electrical interferences among systems. According to these authors, the TN-island-grounding system is the best option to supply shore power to pleasure craft in marinas. This paper substantiates that the TN-island-grounding system allows the development of "hybrid" solutions that lend themselves to the application of either the National Electrical Code, USA, or the International Electrotechnical Commission-European Union codes and standards. This important achievement would contribute to eliminate technical obstacles and discourage market barriers still existing worldwide
Electrical safety of street light systems
No full textStreet light systems are publicly accessible electrical pieces of equipment out of the physical control of who operates/owns them. Street lighting systems typically include low-voltage loads, distributed in a large area, and are collectively protected by the same device. Under fault conditions, hazardous potentials may appear on the metal enclosures of these systems, and expose people to shock hazards. To reduce the risk to an acceptable level, different solutions for the bonding and grounding are available. The Standard IEC 60364 and a current worldwide tendency seem to encourage the use of Class II equipment for the street light systems. Class II components, such as the wiring systems, the light fixtures, etc., have double or reinforced insulation. In this paper, these authors analyze technical alternatives to protect against indirect contact in light of the IEC standards. In order to elevate the level of safety offered by Class II metal poles, the adoption of special circuitry and bonding connections to continuously monitor the double insulation of metal poles is proposed. © 2011 IEEE
Inductive power transfer for automotive applications state-of-the-art and future trends
Full text linkThe paper discusses the status of the development status of the inductive power transmission for automotive applications. This technology is, in fact, gaining the interest of electric vehicle manufacturers as an effective strategy to improve the market penetration of electric mobility. Starting from the origin of this technology, the paper presents an overview of the current state-of-the-art as well as the current research and industrial projects. Particular attention is devoted to the description of a prototypal system for the dynamic inductive power transmission whose goal is to extend the battery range by a fast partial recharging during the movement of the vehicle
Electrical Safety Of Aeronautical Ground Lighting Systems
No full textAeronautical ground lighting (AGL) systems have been developed to deliver warnings and status indications to pilots and maneuvering area vehicle drivers on runways. Their role in preventing the hazard of runway incursions, present in the aviation industry, is therefore crucial. AGL systems basically consist of a primary series lighting circuit, which is supplied at constant current and high voltage (e.g., 5 kV), and AGL transformers supplying ground lights at their secondary sides. Protection of persons against electric shock in AGL systems cannot be conveyed by disconnection of supply as ground faults would cause the out-of-service of the lighting system, thereby compromising the safety of aerodromes; alternative protective measures are therefore employed. In this paper, the authors examine the electrical safety issues present during maintenance of AGL systems, often performed live in order to guarantee the continuity of the service. Experimental measurements on AGL isolating transformers have been also reported in this paper, and possible solutions to improve the electrical safety of operators are proposed
An effective semi-analytical method for simulating grounding grids
No full textThe analytical study of grounding systems is only possible for basic electrodes, i.e., hemispherical and spherical electrodes, rods, and horizontal wires. However, it is normal practice to employ more complex earthing systems, such as grounding grids integrated with rods, in order to obtain lower resistances to ground and improve the electrical safety of substations. This paper introduces a semianalytical (or seminumerical) method, consisting of an analytical approach integrated with a numerical solution, to study grounding grids of complex geometry and their effects on non stratified soils. The algorithm that was created and realized with MATLAB allows the determination of all the quantities of interest for the design and the analysis of such grounding systems, i.e., ground resistance, ground potentials, and distribution of the ground-fault current along the grid's components (i.e., horizontal wires and rods). The model is based on the assumption that conductors forming grids have very small radii if compared with their lengths and that the wires can be considered equipotential cylindrical elements. A verification of the proposed algorithm through a finite-element method has been also carried out to confirm the validity of the results. Exemplary calculations of the ground resistance of grids are included in this paper
Interferences phenomena between separate grounding systems
No full textOne of the main purposes of grounding systems is to safely inject fault currents into the soil; such currents flow through any buried conductive objects (e.g., other earth electrodes) eventually present along their path to the source. As a result, even though grounding systems may be metallically isolated, they become coupled due to the flow of the earth-current and interferences occur. Due to this unwanted coupling, dangerous potentials may arise over the 'passive' electrode, which may expose persons to the risk of electric shocks. This paper proposes a semianalytical approach to evaluate mutual interactions among grounding systems at low frequency, and establishes criteria to evaluate their actual independence. A significant case study of interactions between the substation grid and the safety ground bed in a mining installation is quantitatively discussed
Numerical simulation of heart-current factors and electrical models of the human body
No full textContact with energized parts at different potentials may cause the circulation of body current and the possible inception of the ventricular fibrillation, which is generally considered the most life-threatening effect imposed on the cardiac muscle. The heart-current factors currently present in international standard have been determined thanks to measurements on cadavers, as well as experiments with volunteers. These methodologies are both questionable, as measurements depends on the nature of the probes and their position with respect to the heart; in addition, volunteers cannot obviously be exposed to dangerous levels of currents. Due to the aforementioned difficulties in experimental verifications, the authors propose the use of numerical techniques to investigate the behavior of the human body when is subject to electric fields. This work is based on a mathematical representation of the human anatomy, which takes into account the boundaries of the internal organs. The simulations carried out and documented in this paper, show results that do not entirely match the published IEC heart-current factors; most noticeably, for the pathways hands-feet, right hand-feet and left hand-right foot, the heart-current factors seem to be overestimated by the IEC
Ground-Fault Conditions in Low-Voltage Systems: Potential Differences Between Exposed Conductive Parts
No full textIn low-voltage systems, ground faults do not necessarily involve the actual earth, but fault currents may return to the source via conductors. Such conductors, which provide a clear path toward the source, are defined in the applicable codes and technical standards as equipment grounding conductors or protective conductor
Latent potential differences between exposed-conductive-parts under ground-fault conditions in low-voltage systems
No full textIn low-voltage systems, ground-faults do not necessarily involve the actual earth, but fault currents may return to the source via conductors; such conductors, which provide a clear path toward the source, are defined in applicable codes and technical standards as equipment grounding conductors or protective conductors
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