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As the Navy moves forward with implementing electrochemical energy sources in their power systems, a need to understand the hazards present to electric workers comes to light. Understanding the effects these sources have on arc flash hazards drives the need to study relevant energy sources that are deployed on naval platforms. A 1000-V valve regulated lead acid (VRLA) battery system presents the greatest need to study as incident energy models can suggest dramatic personal protective equipment (PPE) especially with the inclusion of scale factors. As a part of a collaborative effort between the Electric Power Research Institute (EPRI) and the University of Texas at Arlington (UTA) arc flash studies of VRLA battery systems at voltages as high as 936 V have been performed. Findings show that below 800 V, the battery sourced incident energy as high as 0.26 cal/cm2. Above 800 V, incident energy surpassed 1.2 cal/cm2 and approached category 1 PPE (4 cal/cm2). A model derived from this work is used to emphasize the impact enclosure based scale factors have on incident energy estimates. This work has also compared relevant dc incident energy models to the measured incident energy sourced from this battery system.

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The occurrence of an electric arc is an inherent possibility when working in a live line. Thermal risk is considered one of the most relevant risks associated with this type of event, so every worker who performs daily activities in the electricity distribution sector is subject to this risk to a lesser or greater degree. The quantification of the thermal risk is based on estimating the energy generated by the electric arc, and focuses on a surface called incident energy. Therefore, the incident energy estimate is used to define thermal protection strategies applicable to workers who carry out activities in the distribution sector. In light of this, the present work proposes a review of incident energy estimation methods for electric arcs in electric power distribution grids, highlighting the applicability of each of these methods in terms of voltage, short circuit type, and environment. Finally, five case studies are presented in which adequate methods are used to estimate the incident energy. Their results concerning incident energy and selected protective equipment (PPE) are compared. From the review of existing incident energy estimation methods in the literature and the case studies presented, the importance of selecting a suitable method for the type of system analyzed, considering electric, spatial, and intervention aspects, is observed. Finally, considering that the primary objective of incident energy estimation is to determine the need and selection of arc-rated PPE, the selected estimation method must be aligned and integrated with the clothing selection procedures and applicable PPE. [ABSTRACT FROM AUTHOR]

In this work, to investigate the physical vapor deposition (PVD)-deposited TiN coating on the TiN(001) substrate, the process was simulated using the molecular dynamics (MD) method with the 2NN-MEAM (nearest-neighbor modified embedded atom method) potential. The results revealed that the growth mode of TiN film is determined by incident energy. When the incident energy is low, the deposited atoms have weak mobility after momentum transfer with the substrate and cannot fill the vacancy in the TiN film, and thus the TiN film eventually grows in an island shape. When increasing the incident energy, the vibration of atoms on the deposited surface is intensified, and some atoms on the film surface jump. Therefore, the non-thermal diffusion occurs, resulting in defect reduction on the TiN film and forming a lamellar growth with a more continuous and complete film. The growing incident energy continuously reduces the surface roughness of the TiN film. [ABSTRACT FROM AUTHOR]

The ability to achieve a predictable solidification microstructure would greatly accelerate the qualification of the additive manufacturing process. Solidification microstructure control is a challenging issue for the additive manufacturing of metallic components using the laser melting deposition (LMD) method. To obtain desirable microstructure characteristics and mechanical properties, it is essential to research the solidification mechanism of microstructures initiated during the LMD process. In this study, the grain morphology and size of an LMD-fabricated Ti-6Al-4V alloy were predicted using a three-dimensional cellular automaton (CA) model coupled with a finite element (FE) model (CA–FE). First, the temperature distribution and solidification microstructure were established with the multi-scale CA–FE model, and the simulated results were shown to be in qualitative agreement with the experimental results. Moreover, the effects of the process parameters on both the thermal characteristics and the solidification microstructure were identified, and the morphologies and sizes of prior β grains under different laser power levels and scanning speeds were compared. The average grain size of the molten pool was shown to decrease with decreasing incident energy (lower laser power/higher scanning speed), and columnar-to-equiaxed transformation could be achieved under the proper processing parameters. This work will serve as a guide for the optimization and regulation of microstructures in the LMD process. [ABSTRACT FROM AUTHOR]

The occurrence of an electric arc is an inherent possibility when working in a live line. Thermal risk is considered one of the most relevant risks associated with this type of event, so every worker who performs daily activities in the electricity distribution sector is subject to this risk to a lesser or greater degree. The quantification of the thermal risk is based on estimating the energy generated by the electric arc, and focuses on a surface called incident energy. Therefore, the incident energy estimate is used to define thermal protection strategies applicable to workers who carry out activities in the distribution sector. In light of this, the present work proposes a review of incident energy estimation methods for electric arcs in electric power distribution grids, highlighting the applicability of each of these methods in terms of voltage, short circuit type, and environment. Finally, five case studies are presented in which adequate methods are used to estimate the incident energy. Their results concerning incident energy and selected protective equipment (PPE) are compared. From the review of existing incident energy estimation methods in the literature and the case studies presented, the importance of selecting a suitable method for the type of system analyzed, considering electric, spatial, and intervention aspects, is observed. Finally, considering that the primary objective of incident energy estimation is to determine the need and selection of arc-rated PPE, the selected estimation method must be aligned and integrated with the clothing selection procedures and applicable PPE.

NFPA 70E and IEEE 1584 are defining standards for arc flash hazard analysis. Both assume three-phase faults for calculations since three-phase power distribution is predominant in utility and industrial applications; however, arc flash in single-phase systems is excluded. Single-phase faults to neutral or ground or single phase-to-phase faults can occur in a variety of circumstances. Such events may have the potential to produce arc flash and blast that would pose a significant safety concern. This paper describes a recent doctoral research investigation of arc flash in one single-phase configuration. Experiments were sponsored by UL and performed at the Schneider Electric High-Power Laboratory in Cedar Rapids, Iowa. This facility provided a test article; a full suite of voltage, current, and temperature instrumentation; and high-speed video recording. Experimental work revealed incident energy values less than 0.2 cal/cm2 for 240-volt single-phase arc fault events though there was still significant flash and splatter of molten wire residue. 480 V single-phase events produced an order of magnitude greater heat energy, and at 22 kA sustained arcing until interrupted by the test cell controller. Results suggest that 240 V single-phase panels and equipment common in residential and light commercial applications may be at very low risk of yielding arc flash burn-related injuries. However, 480 V single-phase faults can produce levels of incident heat energy known to cause burns, flash, and blast pressure at available fault currents between 10 and 22 kA.

Due to load growth and various load types within the service territory, utilities need to enhance the utilization of substations. In any case, towards the coordinated substation design, the utilization of the transformers’ most total capacity cannot be reduced just because there is a lack of proper coordination between transmission and distribution systems. The transmission and distribution systems’ stability and safe operability must be investigated in a coordinated substation. The critical issues are the asymmetric fault currents on the high voltage and arc-related safety issues on the distribution switchgear at different dynamic loading scenarios. We found that when one 138 kV transmission line and two transformers are energized, with increased dynamic loading, from 40% and above, the substation, as a whole, gets gradually more stressed. Because of the highest amount of fault currents on the 138 kV bus, to avoid CT saturation, we need to consider that three transmission lines are connected, and all three transformers are running at 100% dynamic loading. At this value of dynamic loading, in the 13.2 kV switchgear, the incident energy is 2 cal/cm2, and the arc flash boundary is four feet, which ensures that all workers need to wear the proper arc-rated clothes to work on any de-energized cubicle of the switchgear.

Utility encounters situations like when one out of two power transformers in the substation requires maintenance and only one transformer remains in operation. To meet the load requirements of a maximum number of customers, if not all, the only transformer needs to be overloaded. Due to various load types within the service territory, utilities need to understand the customers' maximum dynamic loading amount to overload a transformer in an emergency. We propose the iteration process with real-world substation data, which considers the concept of a coordinated substation for optimal power flow. We found to what extent the only 138 kV//13.8 kV, 30/40/50 MVA transformer can be safely overloaded beyond its nameplate's maximum rating for a minimum time. Within that time, the utility personnel can work on the substation yard and switchgear room safely and comfortably to bring back the other transformer in operation. We found from the perspective of power flow that with increased dynamic loading, transformer secondary current increases. Therefore, under the maximum dynamic loading condition, we should calculate the asymmetric fault current on the 13.2 kV switchgear bus to select the suitable CTs and develop a protection scheme accordingly.

With the utilization of DC systems increasing, and constant emphasis for worker safety as a top priority for all companies, arc flash feasibility for DC systems is a growing concern. This article details the feasibility of DC arc flash events with experimental scouting tests for a 130 VDC system. Sensitivity studies are experimentally performed on the impact of bus gap distance and bolted fault current level on incident energy. Test results are analyzed and conclusions drawn on the results, in particular incident energies. Details of the tests performed including the setup, procedure, and system parameters are also provided. Theoretical methods of determining incident energy for the testing conditions are also explored. Specifically, these are Doan's and NFPA 70E's maximum power models, and Stokes and Oppenlander's and Paukert's arc resistance models. A comparative analysis of the test results to industry standard, NFPA 70E, and software analysis methods using ETAP, an industry leading software used for arc flash studies, is performed.

To study the protection mechanism of para-aramid fabrics under an electric arc, the structural composition, surface morphology, and thermal properties of an untreated para-aramid fabric and that treated with different incident energy arcs were compared. The intensity of the N-H peak of the para-aramid cellulose amide decreased with increasing exposed arc energy. Moreover, intensities of the C=O peak of the amide bond type I carbonyl and the C-H deformation vibration absorption peak originating from the benzene ring gradually weakened. In contrast, the carbon content of the fabric increased. In the arc deflagration process, the fiber broke and then carbonized and embrittled. With an arc energy of 30.9 cal/cm2, the carbonization degree of the front surface of the fabric increased and was highest at the float line. The initial combustion temperature remained unchanged, and the mass residual quantity gradually increased with increasing arc energy exposed to the fabric. The above results suggest that para-aramid fabric can protect the end user in an arc by carbonization, offering effective assistance in the research and development of personal protective equipment for arc flashes. [ABSTRACT FROM AUTHOR]

This article proposes a new adaptive commissioning methodology for arc flash mitigation in steel manufacturer users considering the Tap-to-Tap varying current consumption. This process is achieved through adaptative protection settings computed to reduce the total clearing time of relays adding the restriction of the incident energy. The proposed methodology carries out the detection of abrupt changes in current consumption to detect Tap-to-Tap change in operation stages of electric arc furnaces. The application of this methodology is performed on a steel manufacturer user and shows the reduction of the incident energy values according to Tap-to-Tap operation cycle. [ABSTRACT FROM AUTHOR]

The 2018 update to the IEEE Std. 1584 Guide for Performing Arc-Flash Hazard Calculations has introduced new electrode configurations that can drastically affect incident energy calculations and labeling. The electrode configurations discussed in this article are: vertical conductors/electrodes inside a metal box/enclosure (VCB), vertical conductors/electrodes terminated in an insulating barrier inside a metal box/enclosure (VCBB), and horizontal conductors/electrodes inside a metal box/enclosure (HCB). It is generally understood that at typical working distances, HCB will produce a higher incident energy than VCBB, which will produce a higher incident energy than VCB with all other parameters equal. However, there is a counter-intuitive trend for the arc-flash boundary, such that the boundary distance for HCB is often lower than the boundary for VCBB and VCB. The electrode configuration will also affect the magnitude of arcing current, which may result in varying fault clearing times depending on which electrode configuration is selected. This article will discuss arcing fault current, incident energy, and arc-flash boundary results for each enclosed electrode configuration that challenge the assumption that HCB will always yield the worst-case incident energy and arc-flash boundary. The results of 50 arc flash studies have been surveyed and presented in this article to supplement and validate observations and conclusions. [ABSTRACT FROM AUTHOR]

The deployment of high-power dc equipment is increasing in solar photovoltaic (PV) plants, but very few studies have quantified dc arc-flash risks. Currently, PV plant owners and operators rely on theoretical, simplified models, such as those in NFPA-70E and other publications, for the assessment of risk associated with dc arc-flash. This article presents an overview of arc-flash risks in a PV system based on a series of field experiments based on IEEE-1584 in two large-scale ground-mounted PV plants. The experiments include various high-power dc equipment of a PV plant, such as central inverters, combiner boxes, recombiner boxes, string inverters, and multiple configurations of electrodes in a 20-in calibration cube. The study reveals that none of the available dc arc-flash models are applicable for a PV plant. This work is an important first step toward developing an improved model that more accurately assesses dc arc-flash risk in a PV plant. [ABSTRACT FROM AUTHOR]

A simplified arc-flash analysis technique that allows for the determination of the settings of overcurrent protective devices and selection of arc-rated personal protective equipment (PPE) based on a reference constant incident energy boundary area is presented in this article. The reference areas are created based on the equations of IEEE Standard 1584-2018 [1], taking into consideration potential variation in the input parameters described in the standard. The method presented in this article provides an efficient and straightforward means to simultaneously consider the effects of varying input parameters on arc-flash calculation results by plotting areas of constant incident energy on a time–current plot. Actual power distribution equipment may have multiple electrode configurations, gaps between conductors, operating voltages, as well as a range of available bolted short-circuit currents and variation in the size of equipment enclosures. The multiple combinations require dozens of simulations to determine the worst-case incident energy levels. Unlike previous implementations of incident energy curves, which were typically single line representations of the incident energy, the plotting of bounded areas (C-area plots) allows for multiple parameter sweeps to determine a band of variation within a defined set of parameter combinations. [ABSTRACT FROM AUTHOR]

Incident energies in photovoltaic (PV) systems are modeled using a variety of methods. These methods are referenced in NFPA 70E and other publications. Direct-current (dc) systems, such as PV systems, may not follow the conventional model used in the present standards. Using experimental data, we will correlate and refine the incident-energy calculations for PV systems. This article proposes a methodology for validating the latest 70E methods for dc PV systems. A forthcoming article will present more of the test results after we improve the test setup and procedures. This article will only discuss dc arcs in PV systems and will not cover arcs in other types of dc systems (e.g., batteries, capacitors, etc.). [ABSTRACT FROM AUTHOR]

In arc flash hazards calculations, protection boundary can be used to gain insight in personnel protection against thermal injuries. Although IEEE 1584-2002 has provided the calculation guide based on tests with the arcing electrodes in a vertical plane, applications where the traditional vertical arrangement is not directly applicable have been drawing more attention over the past few years. Due to the varied thermal behaviors of arc under different equipment configuration and the varied bus connection mode, for the purpose to achieve the adequate protection on arc flash thermal injury, it is necessary to analyze the effect of different electrode geometries on arc flash protection boundary (AFPB). According to the prior work on the development of IEEE 1584-2018, this article fully discusses the impact of electrode geometry on incident energy exposure level and AFPB. With the multiple electrode geometry designed tests, thermal behaviors of arc under different electrode orientation, gap distance, and equipment configurations have been analyzed. According to test results, correction equations were derived under each typical electrode geometry to adjust the AFPB calculation model of IEEE 1584-2002. Through the comparisons, the corrected model can better reflect the actual effects of electrode geometry, meanwhile showing a good ability to provide reasonable AFPB for practical uses. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of incident energy and substrate temperature on the morphological and microstructural properties of TiNi thin films deposited on Ni substrate. The detailed analysis of surface morphology, the interface intermixing, density, and the voids in TiNi thin films was performed by molecular dynamics simulation combined with the second nearest-neighbor modified embedded-atom method interatomic potential (2 NN MEAM). The results indicate that higher incident energy and substrate temperature affect morphological properties of TiNi thin film. When the incident energy ranges from 0.1 to 10 eV, the surface roughness initially increases before eventually decreasing. Regarding the substrate temperature, the roughness decreases initially from 300 K to 700 K, but beyond 700 K, it begins to increase again. In addition, the interface mixing analysis was also affected by incident energy. It is found that, the thickness of the mixing interface was increased as the incident energy increase. This suggests that the growth mode changes from epitaxial to mixing. When the incident energy is higher than 10 eV, the diffusion rate of Ti atoms in the substrate layers is higher than that of Ni atoms. Conversely, at the surface of thin film, the concentration of Ni atoms is higher than that of Ti atoms. However, the substrate temperature has no significant effect on the change in interface thickness. The density of the TiNi thin films shows a significant dependence on the incident energy, but not affected by the substrate temperature. In addition, the result reveal that the increasing both the incident energy and the thickness of thin films reduces the concentration of voids and vacancies. [ABSTRACT FROM AUTHOR]

Studi untuk mengetahui besar busur api yang dihasilkan pada masing-masing switchgear perlu dilakukan untuk mengklasifikasikan kategori energi busur api yang terjadi serta kaitannya dengan PPE (Personal Protective Equipment) yang harus dikenakan pekerja sebagai langkah pencegahan agar terhindar dari jatuhnya korban jiwa. Oleh karena itu perlu dilakukan perhitungan insiden energi arc flash sesuai standar IEEE 1584-2002 serta pengklasifikasian kategori dan alat perlindungan diri yang tepat agar memberikan rasa aman dan nyaman bagi para pekerja sehingga dapat bekerja secara optimal. Studi ini akan coba diterapkan pada sistem kelistrikan di PT. Wilmar Nabati Indonesia, Gresik – Jawa Timur mengingat pentingnya perusahaan tersebut mengamankan peralatan serta pekerjanya dari insiden energy arc flash. Hasil yang didapat pada tugas akhir ini adalah pada tipikal 1 nilai insiden energinya mengalami peningkatan yaitu dari 1.988 cal/cm2 menjadi 8.66 cal/cm2, pada tipikal 2 nilai insiden energi tertinggi 19.596 cal/cm2 turun menjadi 6.00 cal/cm2, pada tipikal 3 nilai insiden energi nya mengalami peningkatan yaitu dari 19.596 cal/cm2 menjadi 36.52 cal/cm2 kenaikan ini disebabkan karena terjadi kesalahan koordinasi rele.

In this paper, we review both ANSI/IEEE and IEC short-circuit calculation methods. We discuss and compare terminology, definitions, and calculation approaches. The advantages and disadvantages of both standards with numerical examples are presented. Identical systems are analyzed using both methods to make a side-by-side comparison of the results. After both methods are introduced in detail and understood, arc flash calculation examples will be provided using IEC short-circuit calculations. Currently, all arc flash calculation methods (including IEEE 1584) focus on three-phase fault currents without being limited to any specific short-circuit standard. In our approach, the IEC method can be effectively used for arc calculations. This approach can be utilized in regions of the world where IEC standards are used for short-circuit calculations. [ABSTRACT FROM AUTHOR]

The irradiation healing process of defective graphene was studied by reactive molecular dynamics simulation of injecting C atoms on a multi-vacancy graphene sheet. We studied the effect of environment temperature and incident energy of injected atoms on healing process of defective graphene. Our simulations show that a relatively high temperature (about 1600 K) is prerequisite for perfect healing of defective graphene. Moreover, an appropriate incident energy for injected atoms (0.16 eV/atom for ∼1800 K) is also necessary for perfect healing, even under a suitable temperature for perfect healing. Defect structures, such as carbon chains and blister-like structures, will occur and hinder the healing process, if the adsorption process (determined basically by incident energy) is faster than the reorganization process (dominated by temperature). In addition, the temperature dependence of reorganization capability of graphene was further studied by molecular dynamics simulation of relaxing an intact graphene sheet with adsorbed atoms. The analysis of the evolution of various micro-structures, emerged during the reorganization simulations, is helpful for deeply understanding the healing mechanism of defective graphene sheet under carbon irradiation. [ABSTRACT FROM AUTHOR]

This paper presents an experimental procedure for determining the probability density function of incident noise energy angular distribution at the building envelope using a microphone array as a measuring device. The motivation for this analysis is the development of a methodology which would provide an insight into the actual structure of the sound field impeding the façades in urban environments. The procedure is based on spatial source localization using a microphone array mounted on the building façade. The results are presented for one characteristic situation in an urban area using different algorithms for space-time signal processing. It is assumed that measurements in different types of façade surroundings, such as canyon and non-canyon streets, would point to the specificities of energy distributions which can be expected in the given situations. [ABSTRACT FROM AUTHOR]

MgO is known to be a material suitable for barrier coating of commercial plasma display panel (PDP) cells owing to its excellent electrical insulating property, good resistance to sputtering, large secondary-electron emission coefficient and high transmittance. It is also a valuable information for improving the efficiency and the lifespan of the PDP. However, the effect of moisture emitted from the wall and phosphor materials of the PDP cells, an Mg(OH) 2 is formed on the top surface of an MgO protective layer. In this work, the Monte Carlo simulation program SRIM-2013 was applied to calculate the sputtering yields of magnesium hydroxide Mg(OH) 2 by low-energy noble-gas ion bombardment. The comparison between results obtained by Monte Carlo simulation and those obtained by experiments is elucidated in this paper. Furthermore, the surface binding energies for MgO and Mg(OH) 2 layers on sputtering yield are discussed. It is found that the sputtering yield of Mg(OH) 2 is generally lower than that of MgO at each incident energy. On the other hand, the sputtering yield depends on the properties of both the incident particle and the target. [ABSTRACT FROM AUTHOR]

This paper deals with the arc flash hazard calculation in large energy storage systems (ESSs), with specific reference to battery energy storage systems (BESSs) and supercapacitor energy storage systems (SESSs). Due to the lack of international harmonized standards and the growing use of large ESSs, the evaluation of arc flash hazard associated with BESS maintenance operation is an interesting subject. In this study, battery circuit models, based on experimental short-circuit tests carried out by TERNA (the Italian transmission system operator) and a simplified supercapacitor circuit model, both coupled with a nonlinear arc resistance model, are used to assess the incident energy related to arc flash in BESSs and SESSs, respectively. Efficient and cost-effective solutions, able to reduce incident energy below the safe value 8 cal/cm2 and based on the installation of fast-acting fuses, are then proposed and discussed. [ABSTRACT FROM PUBLISHER]

The goal of an incident energy analysis is to determine the largest incident energy that a worker could be exposed to at a piece of electrical equipment. This is most commonly done using the IEEE 1584 method. It is a common observation when performing this analysis that minor variations in fault current can result in large changes in a protective device's operating time and the resulting incident energy. This would not be a problem if it was possible to remove all errors from the bolted fault calculation and the arcing fault calculation. Unfortunately, the arcing fault current calculation has some margin of error and the data used in arc flash models are often estimated. A graphical approach to determining the incident energy circumvents these problems and ensures that the worst-case incident energy is determined. This graphical approach is derived from graphs of incident energy based on protective device time–current curves. An examination of the resultant graphs reveals a few maximums in the incident energy curve. These maximums are caused by the protective devices curve, the minimum and maximum arcing fault currents, and any time limitations that are applied. As a result, the locations of these maximums are easily predicted allowing the maximum incident energy to be determined by performing the IEEE 1584 calculation at a few key current values. [ABSTRACT FROM PUBLISHER]

The surface properties of coatings during deposition are strongly influenced by temperature, particle fluxes, and compositions. In addition, the precursor incident energy also affects the surface properties of coatings during sputtering. The atomistic processes associated with the microstructure of coatings and the surface morphological evolution during sputtering are difficult to observe. Thus, in the present study, molecular dynamics simulation was employed to investigate the surface properties of Au/Cu alloy coatings (Cu substrate sputtering by Au atoms) with different incident energies (0.15 eV, 0.3 eV, 0.6 eV). Subsequently, the sputtering depth of the Au atoms, the particle distribution of the Au/Cu alloy coating system, the radial distribution function of particles in the coatings, the mean square displacement of the Cu atoms in the substrate, and the roughness of the coatings were analyzed. Results showed that the crystal structure and the sputtering depth of Au atoms were hardly influenced by the incident energy, and the incident energy had little impact on the motion of deep-lying atoms in the substrate. However, higher incident energy resulted in higher surface temperature of coatings, and more Au atoms existed in the coherent interface. Moreover, it strengthened the motion of Cu atoms and reduced the surface roughness. Therefore, the crystal structure of coatings and the motions of deep-lying atoms in the substrate are not influenced by the incident energy. However, the increase in incident energy will enhance the combination of coatings and the base while optimizing the surface structure.