Flash Energy Research Articles

발전소 아크위험 저감을 위한 전동기 보호방식 개선 연구

In power plants, three phase short circuit current of the high voltage system increased up to 50kA due to lower source impedance which is caused by the large capacity of generators and increased station power capacity. This means that arc flash hazards are much more dangerous in power plants than in general industrial systems.BR This paper presents arc flash energy analysis by using IEEE std 1584 and PowerTools that is one of the power system analysis program, and suggests arc flash hazard mitigation methods by advanced protection schemes of 6.9kV motors which occupy the most of load in power plants.

Focused Research on Arc-Flash Hazards [Electrical Safety

When this column was written, the IFFF Industry Applications Society (IAS) had published four issues of IRPF Industry Applications Magazine and three issues of IRPF Transactions on Industry Applications in 2018. Those issues contained 319 peer-reviewed technical articles and papers. Of those, 24 covered electrical safety topics, and seven of the 24 focused on arc -flash hazards. The seven provided a good picture of the breadth and depth of the work being done to protect our workers, showing the value of the forum provided by the IEEE and IAS for focused research to improve workplace safety. Two of the articles fell in the category of new research, where industry is learning more about arc -flash hazards beyond the limits of previously published works. Many engineers trying to analyze their systems for arc -flash energy have been asking questions about the lower limits of voltage and to what lower limits should they be concerned about arc fl ash.

The Development of Mid-Wavelength Photoresponsivity in the Mouse Retina

ABSTRACTPurpose: Photoreceptors in the mouse retina express much of the molecular machinery necessary for phototransduction and glutamatergic transmission prior to eye opening at postnatal day 13 (P13). Light responses have been observed collectively from rod and cone photoreceptors via electroretinogram recordings as early as P13 in mouse, and the responses are known to become more robust with maturation, reaching a mature state by P30. Photocurrents from single rod outer segments have been recorded at P12, but no earlier, and similar studies on cone photoreceptors have been done, but only in the adult mouse retina. In this study, we wanted to document the earliest time point in which outer retinal photoreceptors in the mouse retina begin to respond to mid-wavelength light.Methods: Ex-vivo electroretinogram recordings were made from isolated mouse retinae at P7, P8, P9, P10, and P30 at seven different flash energies (561 nm). The a-wave was pharmacologically isolated and measured at each developmental time point across all flash energies.Results: Outer-retinal photoreceptors generated a detectable response to mid-wavelength light as early as P8, but only at photopic flash energies. a-wave intensity response curves and kinetic response properties are similar to the mature retina as early as P10.Conclusion: These data represent the earliest recorded outer retinal light responses in the rodent. Photoreceptors are electrically functional and photoresponsive prior to eye opening, and much earlier than previously thought. Prior to eye opening, critical developmental processes occur that have been thought to be independent of outer retinal photic modulation. However, these data suggest light acting through outer-retinal photoreceptors has the potential to shape these critical developmental processes.

Exergoeconomic analysis and optimization of single and double flash cycles for Sabalan geothermal power plant

In this study single and double flash systems were designed to utilize the Sabalan geothermal fluid as a heat source. An Exergoeconomic model was applied on plant’ equipment in order to calculate the thermodynamic and economic performances of the cycles. Parametric analysis was done to examine the effect of important key parameters including flash pressures and steam quality at turbine outlet on plant performance. Optimization process for maximum net power output was carried out on the plant using direct searching method in EES (Engineering Equation Solver). This process aimed to find the optimum flashing pressures corresponding to the maximum potential power output as an objective function. Additionally, the major exergy destruction locations were shown graphically and side by side for both systems to observe the effect of secondary flash process on exergy destruction at each component. Afterward, an environmental study was done in order to calculate the amount of fossil fuel saving and pollutants emission reduction compared to conventional fossil fuel power plants. The result showed that in double flash energy and exergy efficiency were increased from 16.26% and 40.06% to 17.73% and 50.89%, respectively. Moreover, double flash resulted in higher net power output compared to that of single flash (28,838kW vs. 36,055kW) while both cycles were using the same geofluid. Optimization results revealed that thermodynamically optimum cycle could not result the best and lower energy production cost and vice versa. Therefore, the single flash generates electricity within lower price compared to double flash system. Moreover, double flash considerably reduces the required fossil fuel and various pollutants emission more than single flash if they were replaced by fossil fuel power plants with same amount of production.

Pulsed light sintering of silver nanoparticles for large deformation of printed stretchable electronics

Growth of printed electronics has increased the interest in the nanoparticle inks. Research on flexible electronics has expanded not only due to inherent benefits of producing flexible products but also for its high-throughput manufacturability, such as roll-to-toll (R2R) process. Conventional sintering methods cause microcracks and voids in the sintered nanoink film, which lead to subpar performance, and are not suitable for the high-throughput R2R production. Furthermore, these methods are incompatible with many polymer substrates used in flexible electronics due to their low thermal budget. In this study, we present an alternative method utilizing an intense pulsed light (IPL) with a xenon flash lamp to sinter silver nanoink on a polymer substrate. The IPL method is capable of selectively sintering the silver nanoink in milliseconds without damaging the polymer substrates. The silver nanoink was stencil printed on a polydimethylsiloxane (PDMS) specimen. Samples were prepared using five different sintering conditions and tested under uniaxial strain. Three IPL sintering conditions were compared against a non-sintered (NS) and an oven-sintered (OS) conditions. The IPL-sintered samples show a significant improvement in tensile test over NS and OS samples. Samples sintered at 20 J/cm2 of flash energy density and 10 ms of duration were stretched up to 27% strain before losing electrical conductivity. Scanning electron microscopy (SEM) confirms these results showing a reduction in porosity of the sintered nanoink as compared to NS and OS samples.

An Improved Arc Flash Energy Calculation Method and Its Application

In this paper, we describe an improved algorithm for arc flash calculations. This method can be used in any software that performs arc flash calculations to determine the incident energy, arc flash boundaries, and other related parameters for arc flash risk assessment purposes. The method provides a more sophisticated and precise way of calculating short circuit contributions to the fault location. To illustrate the effectiveness of the method, a typical renewable power plant (wind energy) with common types of protection is analyzed. The arc flash risk assessment results are compared in both the conventional way and the presented method. The new approach is called the Integrated Method. This method is an accurate way of modelling the short circuit contribution of the devices, which can potentially change the total short circuit current at the fault location. This Integrated Method considers the decay of the contributing machines and the devices where currents are interrupted due to a protection device. It also accounts for the current decays over time.

A comparison of radiometric calibration techniques for lunar impact flashes

Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ways Bellot Rubio et al. (2000a, b), Yanagisawa et al. (2008), Bouley et al. (2012), Suggs et al. (2014), Rembold and Ryan (2015), Ortiz et al. (2015), Madiedo et al. (2015). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars but this is not typically considered. In our approach, the published color of the comparison star and an estimate of the color of the impact flash is used to correct it to the chosen filter bandpass. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter bandpass according to the stellar atmosphere calibrations of Bessell et al. (1998). In this paper we compare the various photometric calibration techniques and calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the determination of the flux of meteoroids in the 10s of grams to kilograms mass range.

Optocapacitance-Mediated Responses of Excitable Cells: New Developments

Optocapacitance is a technique whereby flash illumination quickly changes membrane capacitance to elicit action potentials (APs) in unmodified (not genetically engineered) excitable cells. Spherical 20-nm gold nanoparticles (AuNPs) interfaced with the plasma membrane serve as light absorbers to induce AP generation in response to 1-ms, 100 μJ, 532-nm laser pulses. Light absorption by the AuNP produces localized heating that changes local temperature by <2⁰C. This increases membrane capacitance, and a resulting depolarizing membrane current (VdC/dt; proportional to the rate of temperature change; Nat. Commun., 2012;3:736) induces opening of voltage-gated sodium channels and thus AP initiation in neurons (Neuron, 2015;86:207-17). Here we present new findings obtained from dorsal root ganglion (DRG) cells, by varying the flash wavelength, light-absorbing particle, and flash duration. Using cylindrical AuNPs (nanorods; 25x94 nm; plasmon absorbance peak at ∼780 nm), a 1-ms, 20 μJ, 785-nm laser pulse was sufficient to elicit APs. A single 1-2 μm graphite particle placed on the DRG cell induced AP generation upon delivery of a 532-nm laser flash of 4 ns duration and 47 nJ energy, representing 130-fold less energy than the 6.2 μJ needed with a 0.5-ms laser pulse. With AuNPs, reduction in flash duration similarly decreased the flash energy required for AP generation. Our data demonstrate the use of near-infrared flashes that penetrate deeper into tissue than green light to elicit APs with light. They also indicate that, in addition to gold and mesoporous silicon (Nat. Mater., 2016;15:1023-30), graphite can enable optocapacitive AP generation. The data furthermore show that, with ∼nanosecond flash durations, APs can be elicited by flashes of ∼nano-Joule energy, i.e., in the range of those used in optogenetic approaches. Support: NIH grants R21-EY023430, R01-GM030376, and the Beckman Initiative for Macular Research.

Thermal and Arc Flash Analysis of Electric Motor Drives in Distribution Networks

The paper presents thermal analysis and arc flash analysis taking care of protection relays coordination settings for electric motor drives connected to the electrical network. Power flow analysis is performed to check if there are any voltage and loading violation conditions in the system. Fault analysis is performed to check the short circuit values and compute arc flash energy dissipated at industrial busbars to eliminate damage to electrical equipment and electrical shocks and hazard to personnel. Computers enable the use of smart algorithms used by electrical engineers in providing accuracy of these actions. A fast and accurate procedure for proper incident arc flash energy computation and overcurrent relays coordination in distribution networks is presented. The paper presents the use of the Arc Flash module for arc flash energy computation during the short circuit on LV and HV busbars with soft motor starters. A sample case of one real network is presented which uses soft motor starters as well as the influence on arc flash energy in one transformer station supplying the industrial network in Bosnia and Herzegovina.

Formation of silicon nanocrystals in silicon carbide using flash lamp annealing

During the formation of Si nanocrystals (Si NC) in SixC1−x layers via solid-phase crystallization, the unintended formation of nanocrystalline SiC reduces the minority carrier lifetime and therefore the performance of SixC1−x as an absorber layer in solar cells. A significant reduction in the annealing time may suppress the crystallization of the SiC matrix while maintaining the formation of Si NC. In this study, we investigated the crystallization of stoichiometric SiC and Si-rich SiC using conventional rapid thermal annealing (RTA) and nonequilibrium millisecond range flash lamp annealing (FLA). The investigated SixC1−x films were prepared by plasma-enhanced chemical vapor deposition and annealed at temperatures from 700 °C to 1100 °C for RTA and at flash energies between 34 J/cm2 and 62 J/cm2 for FLA. Grazing incidence X-ray diffraction and Fourier transformed infrared spectroscopy were conducted to investigate hydrogen effusion, Si and SiC NC growth, and SiC crystallinity. Both the Si content and the choice of the annealing process affect the crystallization behavior. It is shown that under certain conditions, FLA can be successfully utilized for the formation of Si NC in a SiC matrix, which closely resembles Si NC in a SiC matrix achieved by RTA. The samples must have excess Si, and the flash energy should not exceed 40 J/cm2 and 47 J/cm2 for Si0.63C0.37 and Si0.77C0.23 samples, respectively. Under these conditions, FLA succeeds in producing Si NC of a given size in less crystalline SiC than RTA does. This result is discussed in terms of nucleation and crystal growth using classical crystallization theory. For FLA and RTA samples, an opposite relationship between NC size and Si content was observed and attributed either to the dependence of H effusion on Si content or to the optical absorption properties of the materials, which also depend on the Si content.

Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings

A promising method for forming the absorber layer in copper zinc tin sulfide [Cu2ZnSnS4 (CZTS)] thin film solar cells is thermal annealing of coatings cast from dispersions of CZTS nanocrystals. Intense pulsed light (IPL) annealing utilizing xenon flash lamps is a potential high-throughput, low-cost, roll-to-roll manufacturing compatible alternative to thermal annealing in conventional furnaces. The authors studied the effects of flash energy density (3.9–11.6 J/cm2) and number of flashes (1–400) during IPL annealing on the microstructure of CZTS nanocrystal coatings cast on molybdenum-coated soda lime glass substrates (Mo-coated SLG). The annealed coatings exhibited cracks with two distinct linear crack densities, 0.01 and 0.2 μm−1, depending on the flash intensity and total number of flashes. Low density cracking (0.01 μm−1, ∼1 crack per 100 μm) is caused by decomposition of CZTS at the Mo-coating interface. Vapor decomposition products at the interface cause blisters as they escape the coating. Residual decomposition products within the blisters were imaged using confocal Raman spectroscopy. In support of this hypothesis, replacing the Mo-coated SLG substrate with quartz eliminated blistering and low-density cracking. High density cracking is caused by rapid thermal expansion and contraction of the coating constricted on the substrate as it is heated and cooled during IPL annealing. Finite element modeling showed that CZTS coatings on low thermal diffusivity materials (i.e., SLG) underwent significant differential heating with respect to the substrate with rapid rises and falls of the coating temperature as the flash is turned on and off, possibly causing a build-up of tensile stress within the coating prompting cracking. Use of a high thermal diffusivity substrate, such as a molybdenum foil (Mo foil), reduces this differential heating and eliminates the high-density cracking. IPL annealing in presence of sulfur vapor prevented both low- and high-density cracking as well as blistering. However, grain growth was limited even after annealing with 400 flashes. This lack of grain growth is attributed to a difficulty of maintaining high sulfur vapor pressure and absence of alkali metal impurities when Mo foil substrates are used.

Observations of two sprite‐producing storms in Colorado

AbstractTwo sprite‐producing thunderstorms were observed on 8 and 25 June 2012 in northeastern Colorado by a combination of low‐light cameras, a lightning mapping array, polarimetric and Doppler radars, the National Lightning Detection Network, and charge moment change measurements. The 8 June event evolved from a tornadic hailstorm to a larger multicellular system that produced 21 observed positive sprites in 2 h. The majority of sprites occurred during a lull in convective strength, as measured by total flash rate, flash energy, and radar echo volume. Mean flash area spiked multiple times during this period; however, total flash rates still exceeded 60 min−1, and portions of the storm featured a complex anomalous charge structure, with midlevel positive charge near −20°C. The storm produced predominantly positive cloud‐to‐ground lightning. All sprite‐parent flashes occurred on the northeastern flank of the storm, where strong westerly upper level flow was consistent with advection of charged precipitation away from convection, providing a pathway for stratiform lightning. The 25 June event was another multicellular hailstorm with an anomalous charge structure that produced 26 positive sprites in less than 1 h. The sprites again occurred during a convective lull, with relatively weaker reflectivity and lower total flash rate but relatively larger mean flash area. However, all sprite parents occurred in or near convection and tapped charge layers in adjacent anvil cloud. The results demonstrate the sprite production by convective ground strokes in anomalously charged storms and also indicate that sprite production and convective vigor are inversely related in mature storms.

Hybrid Arc Flash Protection Within Electrically Classified Areas

Electrical equipment installed within electrically classified areas-Class I, Division 1 (Zone 1), or Division 2 (Zone 2) locations-require techniques to mitigate flame propagation. Class I, Divisions 1 and 2, or explosion-proof (NEMA 7) techniques are the most commonly used for this purpose. Other techniques, such as enclosed break, flame proof, and restricted breathing, are commonly available methods. A previous PCIC paper (Mendler et al., 2015) explored the electrical arc flash mitigation of the NEMA 7 design. It was found that this design mitigated the electrical arc flash energies, and helped protect personnel from electrical hazard. This paper will explore the percentage reduction in electrical arc flash energies outside the enclosure when an arc occurs inside an enclosure. This will be accomplished using a simpler lighter explosion-protected design. The results will be obtained using an analytical approach, a computational fluid dynamics (CFD) analysis, and with further testing using prototypes that will show enhanced personnel protection.

Arc Flash Hazard Reduction at Incoming Terminals of LV Equipment

Where transformers are used to step down from medium voltage to low voltage, a widely used low-cost solution for primary protection is a fused load break switch. While this device provides good short-circuit protection, it provides limited protection for arcing faults on the transformer secondary and the incoming terminals of the downstream equipment connected to it. Consequently, the arc flash (AF) energy levels in this region can be very high ( $ > 40 \mbox{cal/cm}^2$ ) when compared with the rest of the electrical distribution system and may result in dangerous operating conditions. This paper examines a range of options for primary and secondary protection, identifying those that may result in higher levels of AF energy, and presents guidelines for the selection and application of solutions that have been implemented in existing and new installations, achieving a significant reduction in incident energy levels $( , while addressing concerns for reliability and selective coordination. Piecewise, linear modeling of transformer energization transient response is presented and compared with conventional engineering practice for selecting primary protection. Common assumptions made in modeling instantaneous overcurrent elements will be analyzed, modified, and exploited to achieve reliable application of blocking signals between devices in a protective scheme. Finally, the physical layout of electrical equipment will be discussed as a criteria for optimizing protection schemes to achieve safety by design.

PENGEMBANGAN MEDIA PEMBELAJARAN FISIKA BERBASIS ANIMASI FLASH TOPIK BAHASAN USAHA DAN ENERGI

The use of computers as a learning medium is increasing. But there is still a bit of educators who use the computer as a medium of education facilities. Based on the research of some experts note that by using animation using flash operated by a computer, student learning outcomes improved. Therefore, it is necessary to develop media-based learning physics flash animation subject and Energy Enterprises are using Macromedia Flash 8. Media are developed based on the ADDIE development model, namely Analysis, Design, Development, Implementation, and Evaluation. The program was tested by experts in the study of physics and media experts to determine the feasibility media (program) based on predetermined criteria. After the test results obtained through the medium of learning developed worthy to serve as a medium of learning and can be used in learning.

Lightning channel length and flash energy determined from moments of the flash area distribution

AbstractA widely used approach in observational and modeling studies of NOx produced by lightning is to relate NOx production to the number of flashes, without regard for the distribution of lightning flash sizes. Recent studies have begun to consider channel length and flash size, which is now observable with VHF Lightning Mapping Array data. This study uses a capacitor model for flash energy based on the flash coverage area, which defines a size scale. This flash area is then filled with channel using a fractal method and compared to other methods that estimate length directly from the VHF source locations. In the presence of instrument measurement errors, area‐ and fractal‐based estimates are shown to be more stable estimators of flash length than connect‐the‐dots approaches and therefore are better suited for comparison to NOx production. A geometric interpretation of using vertical profiles of VHF source density to weight the altitude distribution of total channel length is developed. An example of the time series of moments of the lightning flash size distribution is shown for an example case, and some meteorological interpretation is given.

Polycrystalline silicon foils by flash lamp annealing of spray-coated silicon nanoparticle dispersions

A novel technique for the preparation of thin silicon foils (d ≈ 10 µm) starting from silicon nanoparticle dispersions is reported. The basic steps are ultrasonic spray coating of mixtures of silicon nanoparticles and organosilicon compounds and subsequent flash lamp annealing (FLA). The organosilicon compounds are used to stabilize the silicon nanoparticles in dispersion. The FLA induces melting of the silicon nanoparticles which transform into polycrystalline silicon thin films. Parameter adjustment (e.g., pressure, flash duration, flash energy, and substrate temperature) allows for the preparation of thin films as well as free-standing and flexible silicon foils. If the sprayed film thickness reaches a critical value (d ≈ 20 µm) and the FLA is performed under vacuum conditions (5 × 10−3 mbar), then the film peels off from the molybdenum substrate. In a following step, the foil is flashed by FLA from the backside. This method targets thin silicon foils exhibiting thicknesses between 5 and 10 µm. The lateral size of silicon foils depends on the setup used. In this work, samples with a maximum area of approximately 5 × 5 cm2 were produced. The silicon foils were investigated by scanning electron microscopy and spectroscopic ellipsometry to determine thickness, surface structure, and the effective dielectric response. The compositions (Si, C, and O) and the bond characteristics of Si–O and Si–C were analyzed by means of energy dispersive X-ray spectroscopy and X-ray photoemission spectroscopy. Transmission electron microscopy and X-ray diffraction provided the average sizes of the silicon nanoparticles before and after FLA. A rough estimation of the free charge carrier concentration [n el ≈ (1013–1014) cm−3] was possible by electrical four-point probe measurements taking into account information on crystallite sizes.

Modeling of the redox state dynamics in photosystem II of Chlorella pyrenoidosa Chick cells and leaves of spinach and Arabidopsis thaliana from single flash-induced fluorescence quantum yield changes on the 100ns-10s time scale.

The time courses of the photosystem II (PSII) redox states were analyzed with a model scheme supposing a fraction of 11-25% semiquinone (with reduced [Formula: see text]) RCs in the dark. Patterns of single flash-induced transient fluorescence yield (SFITFY) measured for leaves (spinach and Arabidopsis (A.) thaliana) and the thermophilic alga Chlorella (C.) pyrenoidosa Chick (Steffen et al. Biochemistry 44:3123-3132, 2005; Belyaeva et al. Photosynth Res 98:105-119, 2008, Plant Physiol Biochem 77:49-59, 2014) were fitted with the PSII model. The simulations show that at high-light conditions the flash generated triplet carotenoid (3)Car(t) population is the main NPQ regulator decaying in the time interval of 6-8μs. So the SFITFY increase up to the maximum level [Formula: see text]/F 0 (at ~50μs) depends mainly on the flash energy. Transient electron redistributions on the RC redox cofactors were displayed to explain the SFITFY measured by weak light pulses during the PSII relaxation by electron transfer (ET) steps and coupled proton transfer on both the donor and the acceptor side of the PSII. The contribution of non-radiative charge recombination was taken into account. Analytical expressions for the laser flash, the (3)Car(t) decay and the work of the water-oxidizing complex (WOC) were used to improve the modeled P680(+) reduction by YZ in the state S 1 of the WOC. All parameter values were compared between spinach, A. thaliana leaves and C. pyrenoidosa alga cells and at different laser flash energies. ET from [Formula: see text] slower in alga as compared to leaf samples was elucidated by the dynamics of [Formula: see text] fractions to fit SFITFY data. Low membrane energization after the 10ns single turnover flash was modeled: the ∆Ψ(t) amplitude (20mV) is found to be about 5-fold smaller than under the continuous light induction; the time-independent lumen pHL, stroma pHS are fitted close to dark estimates. Depending on the flash energy used at 1.4, 4, 100% the pHS in stroma is fitted to 7.3, 7.4, and 7.7, respectively. The biggest ∆pH difference between stroma and lumen was found to be 1.2, thus pH- dependent NPQ was not considered.

Changes to the turbulent kinematics of a volcanic plume inferred from lightning data

AbstractThe 2009 Redoubt Volcano eruption produced a series of explosive events, the largest of which produced episodes of volcanic lightning similar to thunderstorms. Flash energy spectra were calculated from lightning mapping data collected during the eruption. The spectra were compared to the turbulence characteristics expected from each stage of plume development. Small flash length scales present at early times were associated with the gas thrust and initial convective stages. Increases in flash length scales and flash energy as the explosive events progressed were associated with an increase in volume of the plume. Spectra with a large range in flash length scales (0.2–10 km) and a spectral peak at small flash length scales (&lt; 1 km) were associated with a superposition of spectra from gas thrust, convective, and umbrella/ash cloud regions. An approximate 5/3 power law slope was observed on the order of 10 min after gas thrust forcing had ended and the transition to a drifting ash cloud was underway, which may reflect the dissipating state of the drifting ash cloud.

Modeling of Current-Limiting Circuit Breakers for the Calculation of Short-Circuit Current

A current-limiting circuit breaker (CLCB) can quickly interrupt circuit faults and limit the short-circuit current. Modeling of a CLCB is important for the calculation of short-circuit current and arc flash energy. Based on the analysis of the arc voltage waveforms of CLCBs, a new arc model is derived. The Schwarz arc model and arc length are used to represent the complicated voltages of CLCBs, and arc length is determined from a differential equation. The test results of a commercial CLCB sequentially deployed in a couple of three-phase power systems are studied, and the parameters of the model are obtained. The three-phase faults in the power systems are simulated. The short-circuit currents and voltages of the CLCB are calculated and compared to the test results. The simulation results are in good agreement with the test data, and the proposed model can predict the high-current arcs in CLCBs. These techniques facilitate the calculation of short-circuit currents.