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Parise G.,University of Rome La Sapienza | Parise L.,University of Rome La Sapienza | Mitolo M.,Chu and Gassman Inc.
IEEE Transactions on Industry Applications | Year: 2011

The 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. © 2011 IEEE. Source


Mitolo M.,Chu and Gassman Inc. | Freschi F.,Polytechnic University of Turin | Tartaglia M.,Polytechnic University of Turin
IEEE Transactions on Industry Applications | Year: 2011

The bonding of electrical equipment plays a crucial role in maintaining the same potential between conductive parts likely to be energized and conductive parts liable to introduce a "zero" potential into the premises. Voltage rises between such parts are unsafe, as they may induce harmful currents through the human body, the magnitude of which may vary depending on a number of factors. This paper seeks to clarify the bonding requirements in low-voltage electrical systems, by using the concepts of exposed conductive parts and extraneous conductive parts, present in the International Electrotechnical Commission standards, applied to a proposed electric shock model of the human being. With the purpose of reducing the consequences of electric contacts, the authors propose objective criteria to decide whether conductive "dead" objects and enclosures of electrical equipment must be bonded or not. © 2011 IEEE. Source


Mitolo M.,Chu and Gassman Inc. | Freschi F.,Polytechnic University of Turin | Pastorelli M.,Polytechnic University of Turin | Tartaglia M.,Polytechnic University of Turin
IEEE Transactions on Industry Applications | Year: 2011

The ecodesign of modern residential and commercial low-voltage systems implements energy and equipment cost savings, optimizing the size of the distribution system without compromising its functionality or causing environmental contamination, including electromagnetic pollution. Protection of persons against shock hazards should be increased, and the electrical interferences among power systems should be reduced. To achieve the aforementioned improvements, a possible ecodesign calls for an earthing system utilizing single-phase separation transformers installed in the unit and grounded at the midpoint of their secondary side. The introduction of a source of magnetic fields into the premises at the power frequency of 60/50 Hz [i.e., extremely low frequency (ELF)] might expose persons to potential adverse health effects, as well as sensitive electronic equipment to disturbances. This paper seeks to clarify this matter by evaluating the ELF magnetic fields as produced by the user's own transformer and by other units eventually present in the vicinity. © 2011 IEEE. Source


Mitolo M.,Chu and Gassman Inc. | Tartaglia M.,Polytechnic University of Turin
IEEE Transactions on Industry Applications | Year: 2012

At the occurrence of phase-to-ground faults, abnormal levels of thermal energy I 2t, due to the Joule effect, will be developed during the clearing time that protective devices take to operate. The I 2t, also referred to as specific energy or Joule Integral, is accumulated within the elements forming the fault loop, such as the protective conductors (also referred to as equipment grounding conductors), responsible to return ground-fault currents to the source. As a consequence, the temperature of these conductors elevates and may exceed, in the case of an incorrect design, the maximum value that their insulation can withstand. This dangerous situation can cause the failure of the conductor insulation and/or trigger fires in neighboring materials. The maximum I 2t that protective conductors can endure is, therefore, crucial in order to guarantee the electrical safety. The parameters on which the maximum I 2t depends are described by the factor k 2, which will be herein discussed and analytically evaluated. The intention of the authors is to provide a theoretical support to the Power Systems Grounding Working Group of the Technical Books Coordinating Committee IEEE P3003.2 "Recommended Practice for Equipment Grounding and Bonding in Industrial and Commercial Power Systems"; the working group is currently elaborating a dot standard based on IEEE Standard 142-2007, also referred to as the Green Book. To this purpose, a comparison with existing formulas, currently present in codes, standards of the International Electrotechnical Commission and of the IEEE, as well in the literature, will be also presented. © 2006 IEEE. Source


Tartaglia M.,Polytechnic University of Turin | Mitolo M.,Chu and Gassman Inc.
IEEE Transactions on Power Delivery | Year: 2010

At the occurrence of three-phase or single-phase faults, abnormal levels of thermal energy are developed during the time taken by protective devices to clear them. By conservatively assuming an adiabatic process, all of the thermal let-through energy I2t, also referred to as Joule Integral, is accumulated within the components involved in short circuits; therefore, the temperature of their conductive materials is elevated. The thermal energy is proportional to the square of the short-circuit current. Evaluating the prospective I2t is, therefore, crucial in order to assess the short-circuit capability of cables and busways to withstand the thermal stress without failing or triggering fires in neighboring materials. In this paper, in the general case of resistive-inductive circuits, methods to evaluate the Joule Integral and to perform the assessment will be provided. The differences for power frequencies of 50 and 60 Hz are also shown. © 2010 IEEE. Source

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