showing 19 related works from this author
Legal Liability of Professional Engineers: The Case of a Fire at a Shopping Center
2019
In this paper, the authors discuss the legal liabilities of the professional engineer as both the engineer of record of a project and the construction site manager. In particular, this paper analyzes the case of a fire at an end-user MV/LV substation of a shopping center in Italy, occurred a few years after maintenance works on the electrical installation. The professional engineer who had designed and overseen the construction of the substation was accused of criminal negligence. The authors through the examination of applicable technical standards, as well as of safety regulations, demonstrate that the professional engineer had acted diligently and that there was no ground for the neglige…
On the de-energization of over-head low-voltage lines under high-impedance fault conditions
2018
Downed distribution conductors in overhead distribution systems, may not be a concern for equipment, but greatly challenge the safety of persons, as well as the integrity of properties. Upstream overcurrent protective devices may not be able to detect the magnitudes of fault currents resulting from these high-impedance faults. Even though protective devices capable to detect such faults have been available on the market, not all the utilities have equipped their stations with these products, likely due to the costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for the low-voltage over-head lines with neutral wire. Such solution includes a …
Forensic Analysis of Fire in a Substation of a Commercial Center
2020
In this article, the authors discuss the legal liabilities of the professional engineer as both the engineer of record of a project and the construction site manager. In particular, this article analyzes the case of a fire at the end-user medium voltage–low-voltage (MV–LV) substation of a shopping center in Italy, which occurred a few years after the maintenance works on the electrical installation. The professional engineer who had designed and overseen the construction of the substation was accused of professional negligence. The authors through the examination of applicable technical standards, as well as of safety regulations, demonstrate that the professional engineer had acted diligen…
A Cost-Effective Solution for Clearing High-Impedance Ground Faults in Overhead Low-Voltage Lines
2019
Downed distribution conductors in overhead distribution systems may not be a concern for equipment but greatly challenge the safety of persons, as well as the integrity of properties. Standard overcurrent protective devices may not be able to detect the magnitudes of currents resulting from high-impedance ground faults. Sophisticated relays able to detect high-impedance ground faults have been available to electric utilities. However, their implementation is rather uncommon, especially in developing countries, most likely due to their costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for low-voltage overhead lines with neutral wire. This…
A Comparison of Special Bonding Techniques for Transmission and Distribution Cables under Normal and Fault Conditions
2021
In this article, a review of the existing special bonding techniques for medium voltage and high-voltage cables is presented. Special bonding techniques have the purpose of reducing sheath currents, thereby limiting copper losses and the reduction of the ampacity of cables. The literature review shows various bonding techniques and how these have evolved over the years thanks to new technologies. Simulations of each technique are performed in MATLAB/Simulink, to compare their strengths and drawbacks both under normal conditions and in the presence of a single-line-to-ground fault.
A Model for Assessing the Magnitude and Distribution of Sheath Currents in Medium and High-Voltage Cable Lines
2020
In this article, the authors discuss a simulation model to study the effect of cross-bonding of metallic sheaths, and/or nonmagnetic armors, of single-core medium- and high-voltage cables in the same circuit. In single-core cables, the resistive losses due to the induced circulating currents in cable sheaths or armors cause an increase of the cable temperature, which therefore reduces its ampacity. This is a serious issue affecting the distribution and transmission lines. In addition, the risk of electric shock due to induced voltages may be present if a person is in contact with the armor/sheath at its unbounded end. For these reasons, special bonding techniques of metal sheaths are employ…
Safety Protocols for Forensic Inspections in the Time of COVID-19: An Approach to Protect Practitioners
2022
The COVID-19 pandemic has impacted the entire world in ways that were unimaginable in 2019. It has changed how professionals work and interact with one another. To ensure the safety of experts and attorneys, forensic inspection procedures must evolve while still providing a reliable foundation for expert testimony. Traditional field inspections require attendees to be physically present and in generally close proximity. Inspecting artifacts may also require that individual components be serially examined by multiple experts, which increases the risk of transmitting the disease. The authors propose a new approach to forensic inspections aimed at protecting consultants from the biological ris…
Forensic Inspections in the Time of Covid-19
2021
The global pandemic of COVID-19 has impacted the entire world in ways that were unimaginable months ago. It has changed how professionals work and interact with one another. To ensure the safety of experts and attorneys, also forensic inspection procedures must evolve, while still providing a reliable foundation for an expert testimony, relevant to the task at hand. Traditional field inspections require attendees to be physically present and generally in close proximity. Inspecting artifacts may also require that individual components be serially examined by multiple experts, which increases the risk of transmitting the disease. The authors propose a new approach to forensic inspections aim…
Fire risk assessment and cable selection for enduser substations
2017
This paper examines the issues related to fire risk assessment in end-users substations. Fires in substations may be caused by electrical faults, overvoltages, lack of maintenance, etc. It is crucial that fires be confined within the substation, and not propagate into the adjacent environment, where their effects may put at risk personnel, as well as other properties. To reduce this risk of propagation, the choice of cables and the related wiring methods are crucial; in addition, the characteristics of cable chases that route cables from the substation to adjacent rooms is very important. IEEE and IEC fire protection standards for end-user substations are herein discussed, with emphasis on …
Electrical Safety Analysis in the Presence of Resonant Grounding Neutral
2019
The resonant grounding is one of the possible methods of the system neutral grounding for the medium voltage distribution. IEEE standards do define this grounding configuration, but important advantages and drawbacks of the resonant grounding might not be fully known, due to its rather uncommon application in North America. On the other hand, resonant grounding in Europe is imposed by the increased requirements for power quality, especially for medium-voltage (MV) industrial users, imposed to electric utilities by regulatory authorities, with the purpose to protect the interests of users and consumers. Level of the continuity of the service, magnitude and phase of ground-fault currents, mag…
A Model for the Study of Sheath Currents in Medium Voltage Cables for Industrial Application
2020
In this paper, the implementation of a simulation model for studying the effect of cross-bonding of metallic sheaths and/or non-magnetic armor of single-core medium voltage cables in the same circuit is discussed. With the use of single-core cables, the resistive losses due to the induced circulating currents in cable sheaths or armors causes an increase of cable temperature that reduces its ampacity. In addition, the risk of electric shock due to induced voltages may be present if a person is exposed to the armor/sheath at the unbounded end. For this reason, special bonding techniques are used to significantly reduce these currents. The authors have implemented a model that could be used t…
Short-circuit Calculations in Hybrid AC/DC Microgrids
2022
In this paper, the issues related to short-circuit calculations in hybrid AC/DC microgrids are discussed. The reference standard for short-current calculations in DC systems is the IEC 61660, which provides a mathematical formulation of the problem. The standard only includes radial DC grids and does not consider a more complex system, such as meshed DC systems or a hybrid AC/DC microgrid. This paper proposes a generalized approach that can be used independently of the characteristics of the hybrid system. The proposed approach is applied to two test microgrids and the results are compared with those obtained simulating the same grids with Neplan 360.
Electrical Safety of Resonant Grounding
2019
The resonant grounding is one of the possible methods of system neutral grounding for the medium-voltage distribution. IEEE standards do define this grounding configuration, but important advantages and drawbacks of the resonant grounding might not be fully known, due to its rather uncommon application in North America. On the other hand, resonant grounding in Europe is imposed by the increased requirements for power quality, especially for medium-voltage industrial users, and imposed to electric utilities by Regulatory Authorities, with the purpose to protect the interests of users and consumers. Level of the continuity of the service, magnitude and phase of ground-fault currents, magnitud…
A General Methodology for Short-circuit Calculations in Hybrid AC/DC Microgrids
2023
In this paper, the issues related to short-circuit calculations in hybrid AC/DC microgrids are discussed. The reference standard for short-current calculations in DC systems is the IEC 61660, which provides a mathematical formulation of the problem. The standard only includes radial DC grids and does not consider a more complex system, such as meshed DC systems or a hybrid AC/DC microgrid. This paper proposes a generalized approach that can be used independently of the characteristics of the hybrid system. The proposed approach is applied to four test microgrids with different distributed sources and number of nodes and the results are compared with those obtained simulating the same grids …
A Methodology for Protection of Trees Against Lightning Strikes as a Measure to Prevent Fires and Loss of Human Life
2021
Some regions may be characterized by a very low annual lightning ground flash density, and yet lightning strikes seem to have been in those areas the cause of widespread wildfires in forested areas. Due to global climate change, these occurrences seem to be an increasing threat. In this paper, the authors discuss the withstand capability of trees against lightning and introduce the criteria for the deployment of tree lightning protection systems (TLPS) to protect forested areas, where deemed necessary by the tree risk assessment. This work analytically identifies the critical trunk radius of the tree below which the tree may explode in the case of a lightning strike and ignite the surroundi…
On the Interconnections of HV–MV Stations to Global Grounding Systems
2019
The interconnection of grounding systems of HV-MV stations via the armors of medium voltage cables, is herein analyzed to verify the effects on touch voltages in ground-fault conditions. The major contributions of this paper are two: the analysis of the impact of an HV ground-fault on a global grounding system (GGS), and the analysis of the parameters that may affect safety due to the interconnection between HV-MV stations and the GGS. The authors have analyzed cases when the connection of an HV-MV station to a GGS improves safety, and then may introduce hazards under ground-fault conditions. Two main issues are herein discussed: 1) the transfer of dangerous voltages to substations, due to …
Protection of Trees against Lightning Strikes as a Measure to Prevent Fires and Loss of Human Life
2021
Lighting strikes have been the catalyst of massive uncontrolled fires in areas of combustible vegetation. In some regions, lightning strikes may be a relatively unusual occurrence (e.g., California), but instead they seem to have become a major contributor to the propagation of wildfires, as a byproduct of climate change. Given such unusual weather, wildfires originating from lightning are an increasing threat. In this paper, the authors discuss the withstand capability of trees against lightning and introduce a proactive approach to prevent wildfires by the deployment of tree lighting protection systems (TLPS) to protect forested areas, where deemed necessary by the tree risk assessment.
A Comparison of Special Bonding Techniques for Transmission and Distribution Cables
2020
In this paper, a review of the existing special bonding techniques for medium voltage (MV) and high-voltage (HV) cables is presented. Special bonding techniques have the purpose of reducing sheath currents, thereby limiting copper losses and the reduction of the ampacity of cables. The authors present a literature review to identify various bonding techniques and how these have evolved over the years thanks to new technologies. Simulations of the most used techniques have been performed in Matlab/Simulink, to compare their strengths and drawbacks.
Interconnections criteria of grounding grids in global grounding systems
2018
A Global Grounding System is defined as the combination of local grounding systems, obtained by their interconnection, which ensures, thanks to their proximity, that no dangerous touch voltages can arise. The interconnection of grounding systems via the armors of the MV cables, between secondary substations and HV/MV stations is herein analyzed to verify the effects on touch voltages in ground-fault conditions. In particular, two main issues are discussed: 1) the transfer of dangerous voltages to secondary substations, due to ground-faults occurring at the HV/MV station; 2) the reduction in the magnitude of the ground potential rise due to ground-fault conditions at secondary substations, t…