Chu and Gassman Inc.

Middlesex, NJ, United States

Chu and Gassman Inc.

Middlesex, NJ, United States

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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.


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.


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.


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.


Mitolo M.,Chu and Gassman Inc. | Sutherland P.E.,General Electric | Natarajan R.,Burns and McDonnell
IEEE Transactions on Industry Applications | Year: 2010

Due to increased load demands and reduced incentives to build new transmission lines, energy companies are increasing power flows on the existing transmission assets, which will increase the fault current levels (for both three-phase and phase-to-ground faults) throughout the power system. New generation sources to be added at the transmission and distribution network will increase fault current intensities. It is crucial for the users of industrial facilities to be aware of increased ground-fault current magnitude at the service entrance and of the actual condition of the grid. The protection that ground grids provide against step and touch potentials is only good up to the expected level and duration of ground-fault currents, as originally communicated by the electric utility in the design phase. In addition, thermal and mechanical stresses to the customer's ground grid and ground grid connections can increase the grid's resistance to ground and, at the same time, fault potentials. In order to prevent these problems from occurring, a ground grid assessment, utilizing field and utility updated data, should be carried out on a regular basis. This paper will illustrate a European Committee for Electrotechnical Standardization (CENELEC) approach to ground grid design, aimed to maximize the electrical safety under ground fault. In addition, case studies will be included, showing how high fault currents have damaged ground grids and what repairs are possible. © 2006 IEEE.


Parise G.,University of Rome La Sapienza | Mitolo M.,Chu and Gassman Inc.
European Transactions on Electrical Power | Year: 2012

TN-Island grounding system is an effective way to both protect persons from shock hazard in installations with limited demand load and greatly limit electrical interferences among systems. This distribution system, which utilizes separation transformers, grounded on the secondary sides, allows one to supply loads broken into "islands" as independent electrical areas. TN-Island fits best the supply of electrical installations in particular locations like moored pleasure crafts in marinas, fish farms, fish tanks, refrigerated containers in seaports, data centers, and construction sites. Additionally, by introducing the TN-Island to provide power to dwelling units, regardless of their existing electrical distribution system, we can improve electrical safety and, at the same time, increase reliability since the "islands" are not electrically interfering with each other. Last but not least, the TN-Island system, allows one to develop "hybrid" systems just for restricted electrical areas, for example, dwelling units, and can lead to a free choice of systems and standards (i.e., NEC-USA and IEC-UE). This would eliminate technical obstacles and discourage market barriers. Such a process is as crucial as it is inevitable, as a consequence of the current world globalization. This could promote electrical safety, better functionality, and lower costs. Copyright © 2011 John Wiley & Sons, Ltd.


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.


Mitolo M.,Chu and Gassman Inc.
IEEE Transactions on Industry Applications | Year: 2010

The application of residual-current principle, as carried out by zero-sequence current protective devices, is one of the most efficient ways to reduce the hazard of electric shock in case of a failure of the equipment's basic insulation to ground. Highly sensitive and regularly tested residual-current-operated circuit breakers without integral overcurrent protection (RCCBs) devices are rightfully recognized worldwide by standards and codes as an effective means to protect persons against direct and indirect contact with energized parts by disconnecting the supply in a timely fashion. These devices are also referred to as ground-fault circuit interrupters. The protective action of the RCCBs, however, can be nullified not only due to internal malfunctions of the device but also due to particular ground-fault conditions. In these dangerous situations for persons, for example, accidental direct contact with two parts at different potentials, the residual current flowing through the RCCB is below its residual operating value, and therefore, it cannot trip. This hazardous circumstance exposes persons to dangerous touch voltages despite the presence of an efficient protective device, which cannot be blamed for not intervening. This paper seeks to clarify these particular fault conditions occurring even in the presence of healthy RCCBs. © 2010 IEEE.


Mitolo M.,Chu and Gassman Inc.
IEEE Transactions on Industry Applications | Year: 2010

Multiple grounded neutral systems require that, on most land-based ac current service installations, the bonding conductor used to connect the non-current-carrying metal parts of equipment, the system grounded conductor (neutral), and the grounding electrodes be bonded together at the service entrance box. Users thus share their ground with the serving utility's neutral ground. This interconnection, although functional, poses some distinctive problems to utility companies as well as to users, which this paper seeks to clarify. © 2010 IEEE.


Mitolo M.,Chu and Gassman Inc.
IEEE Transactions on Industry Applications | Year: 2010

Antennas, if present on roofs, are, usually, the most prominent part of edifices. Grounding their metal supports is, generally, considered an effective means of protection of the structure against the effects of lightning strokes, eventually attracted by the antennas themselves. The antenna's mast and the down conductor are incorrectly assumed capable of safely draining to ground the lightning current flowing at the point of strike. This, supposedly, would prevent both hazard for people and damage to the building and electrical equipment situated inside of it. This paper will substantiate how the sole grounding of the antenna's mast can instead result in lowering the safety of the edifice, and, thereby, expose users to the hazard of dangerous electrical sparking (flashover) and possible fires. © 2010 IEEE.

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