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The main component of vacuum interrupters responsible for ensuring the correct flow of current is the contact system. In a vacuum environment, due to the higher values of the mean free path of electrons and particles in the contact gap, the material and condition of the contacts exert the greatest influence on the development of the arc discharge. To accurately analyze the phenomenon of discharge development in vacuum insulating systems, the authors conducted a time-lapse photographic analysis of a vacuum electric arc. For this purpose, they used a test setup comprising a discharge chamber, a vacuum pump set, a power and load assembly, an ultra-high-speed camera, and an oscilloscope with dedicated probes. The measurement process involved connecting the system, determining the power supply, load, and measurement parameters and subsequently performing contact opening operations while simultaneously recording the process using the oscilloscope and ultra-high-speed camera. An analysis of a low-current vacuum arc in a residual helium gas environment, with a pressure of p = 1.00 × 101 Pa was carried out. Different phases of vacuum arc burning between electrodes in the discharge chamber were identified. In the stable phase, the arc voltage remained constant, while in the unstable phase, the arc voltage increased. The results of the time-lapse analysis were compared with the characteristics recorded by the oscilloscope, revealing a correlation between the increase in vacuum arc voltage and the intensity of flashes in the interelectrode space. The movement of microparticles ejected from the surface of the contacts—either reflecting or adhering to one of the electrodes—was observed. This analysis provides a deeper understanding of the processes involved in discharge formation and development under reduced pressure conditions. Understanding these mechanisms can support the design of vacuum interrupters, particularly in the selection of suitable contact materials and shapes. [ABSTRACT FROM AUTHOR]

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.

An arc flash and fire in the secondary compartment of an industrial facility utility transformer resulted in destruction of newly installed electrical metering equipment. Inherent to this type of event are two loss-ofevidence challenges: extremely high heat burns or melts everything nearby, and urgency to restore normal operation may prevent comprehensive examination of the scene. The facility contractor's operations staff conducted an initial root cause analysis. The contractor's management called on an external forensic team to provide an independent assessment. Having an established investigation methodology allows the forensic examiner to better understand what was, and was not, evaluated by facility staff and prevents confirmation biases. This paper examines the facility's report, addresses shortcomings in its conclusions, and goes on to detail the methods and reasoning behind the forensic team's findings. The methodology presented in this paper is applicable to a wide range of industrial electrical fires. [ABSTRACT FROM AUTHOR]

The arc flash is one of the main hazards that electrical energy presents. Due to its importance, arc flash research has focused on Alternating Current (AC) electrical systems. However, a considerable increase in Direct Current (DC) systems has been observed, particularly in integrating new technologies such as generation with non-conventional energy sources, electric vehicles, and energy storage systems. Direct Current (DC) installations are exposed to the same dangerous situations as Alternating Current (AC) installations, so that no electrical installation can guarantee an arc flash-free situation. In this paper, calculations required to estimate the incident energy in AC and DC systems are methodologically described under guidelines established by the most current standards: IEEE Guide for Performing Arc-Flash Hazard Calculations of 2018 and NFPA E70 Standard for Electrical Safety in the Workplace of 2021. This work uses a case study of a hospital facility on the Island of San Andrés, Colombia. [ABSTRACT FROM AUTHOR]

The importance of the quality and continuity of electricity supply is increasingly evident given the dependence of the world economy on its daily and instantaneous operation. In turn, the network is made up of power transmission lines. This study has been carried out based on the Scopus database, where all the publications, over 5000 documents, related to the topic of the power transmission lines have been analyzed up to the year 2022. This manuscript aims to highlight the main global research trends in power transmission lines and to detect which are the emerging areas. This manuscript cover three main aspects: First, the main scientific categories of these publications and their temporal trends. Second, the countries and affiliations that contribute to the research and their main research topics. Third, identification of the main trends in the field using the detection of scientific communities by means of the clustering method. The three main scientific categories found were Engineering, Energy and Computer Science. This research is most strongly developed in China, as the top 10 institutions are from this country, followed by USA and in third place by Russia. Twelve lines of research have been detected: Line Inspection, Leakage Current, Magnetic Fields, Fault Location, Icing, Lines Design, Natural Disasters, Temperature, Half-wave, Arc Flash, Pattern Recognition, and Artificial Intelligence. This research will open new perspectives for future research on power transmission lines. [ABSTRACT FROM AUTHOR]

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.

The empirical model of IEEE Standard 1584 defines arc flash incident energy and arc-flash boundary. This article assumes as reference the empirical model that compares with the spherical model of the incident energy emission and classifies the deviations. The new approach allows a physical approach to the phenomenon, to identify characteristic parameters as the arc flash intensity, and to analyze the distribution of the incident energy applying the “point-by-point” method on flat surfaces exposed to arc flash, as a simulation of the human body. This method allows us determining isoflash surfaces that collect points at different distances in the space, allows us characterizing the behaviors of electrodes configurations and estimating the prospective body surface area affected by lesions. [ABSTRACT FROM AUTHOR]

Injuries sustained while performing electrical work are a significant threat to the health and safety of workers and occur frequently. In some jurisdictions, non-fatal serious incidents have increased in recent years. Although significant work has been carried out on electrical safety from a human factor perspective, reviews of this literature are sparse. Thus, the purpose of this review is to collate and summarize human factors implicated in electrical safety events. Articles were collected from three databases (Scopus, Web of Science, and Google Scholar), using the search terms: safety, electri*, human factors, and arc flash. Titles and abstracts were screened, full-text reviews were conducted, and 18 articles were included in the final review. Quality checks were undertaken using the Mixed Methods Appraisal Tool and the Critical Appraisal Skills Program. Environmental, individual, team, organizational, and macro factors were identified in the literature as factors which shape frontline electrical worker behavior, highlighting the complexity of injury prevention. The key contributions of this paper include: (1) a holistic and integrated summary of human factors implicated in electrical safety events, (2) the application of an established theoretical model to explain dynamic forces implicated in electrical safety incidents, and (3) several practical implications and recommendations to improve electrical safety. It is recommended that this framework is used to develop and test future interventions at the individual, team, organizational, and regulator level to mitigate risk and create meaningful and sustainable change in the electrical safety space. [ABSTRACT FROM AUTHOR]

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.

The electric discharge across a varistor granule filled air gap under a fast‐rising voltage pulse was investigated for surge protection applications. The effects of temperature and pressure on the arc and the electrical conduction were analyzed by the characteristic changes in voltage waveforms triggered by a fast‐rising high voltage pulse. In addition to the gap size, experimental results show that competing mechanisms among arc conduction, conduction through the varistor granule network, thermionic emission from Joule heating at granule‐to‐granule contact points, and the magnitude of the switching voltage dictate the maximum surge protection voltage for the filled air gap. Experimental evidence indicated that accumulated degradation was created at small contact points between varistor granules by repetitive assaults from longer duration, high voltage pulses. The uniqueness of using varistor over other dielectric granules in an air gap for surge protection is identified and discussed. [ABSTRACT FROM AUTHOR]

As power distribution systems become increasingly interconnected and concentrated with distributed energy resources (DER) and high potential equipment, effectively avoiding the medium-low voltage caused safety risk, drawing more attention. Therefore, the accurate, fast, and reliable preemptive arc detection and location method is essential to be developed. However, due to the issues such as low sensitivity, delayed detection, complex structure, and susceptible to interference by other sources, the traditional approaches are not up to the detection and location job, for weak system source and high arcing resistance featured medium-low voltage arc flash. To overcome the limitations, this article explores a novel arc flash preemptive detection and location mechanism. With the application of geometric distribution analysis on magnetic density flux and current density, mathematical modeling incorporated magnetohydrodynamic approach is developed. With a series of actual cases incorporated simulations were performed, the criterion of arc initiation and concisely numerical model on arc fault location estimation is derived, which shows a good ability to catch the transient dynamics of arcing current in the early initiating stage, and also proves the reliability and accuracy on fast detection and location uses. These results offered valuable information for medium-low arc fault mitigation and hazard prevention. [ABSTRACT FROM AUTHOR]

Modern awareness of workplace hazards has created a range of safety standards and best practices now accepted and implemented in the design and construction of many types of industrial and commercial installations. Prevention through Design (PtD) concepts are well understood and commonly applied in the design of many facilities where dangerous chemicals or dangerous concentrations of energy are a required part of the process.  Heightened awareness of electrical hazards over the last two decades has resulted in a greater understanding of the arc flash hazard and shock hazard and in many methods and tools to control the associated risks. However, the PtD concepts well understood and implemented in other aspects of industrial facility design may not be well understood or are often not implemented at the electrical infrastructure's design and construction stage within industrial or large commercial facilities. This article will discuss the correlation between PtD and industrial accidents and how PtD concepts applied to electrical infrastructure can improve modern facilities' safety and productivity. [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]

Arc flash hazard prediction methods have become more sophisticated because the knowledge about arc flash phenomenon has advanced since the publication of IEEE Std. 1584-2002. The IEEE Std. 1584-2018 has added parameters for more accurate arc flash incident energy (IE), arcing current, and protection boundary estimation. The parameters in the updated estimation models include electrode configuration, open circuit voltage, bolted fault current, arc duration, gap width, working distance, and enclosure dimension. The sensitivity and effect changes of other parameters have been discussed in the previous literatures. This article explains the fundamental theory on the selection of electrode configurations and performs sensitivity analysis of the enclosure dimension that have been introduced in the IEEE Std. 1584-2018. According to the newly published model for IE estimation, the IE between vertical conductors inside a metal box (VCB) and horizontal conductors inside a metal box (HCB) can differ by a factor of two with other parameter constants. Using HCB as the worst-case scenario to determine the personal protection requirements may not be the best practice in all circumstances. This article provides guidance for electrode configuration selection and a sensitivity analysis for determining a reasonable engineering margin when actual dimension is not available. [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]

Maximum arc flash energy is seen at the secondary of transformers before the first protective device. Reducing transformer primary protection trip times to cool this “hot spot” starts with quicker tripping on the secondary. Zone selective interlocking (ZSI) is a proven means of avoiding the delays of traditional coordination time intervals but interlocking of all devices within a system can raise concerns about construction and testing complications. How much of an arc flash benefit would it be to interlock only main and tie breakers where interlock capable communication exists for automated transfer scheme functions. To determine benefits, arc flash hazards are first reduced to the extent possible with traditional measures. Communication elements are analyzed to determine those having the speed and reliability required for protection quality interlocking. ZSI is then applied between main and tie breakers to demonstrate how the hazards of the arc flash hot spot can be brought under control. [ABSTRACT FROM AUTHOR]

This article examines several electrical incidents and compares them to what the NFPA 70E and the CSA Z462 Standards would require and what actually happened in the field. Estimates range from 80% to 95% as to how many incidents are caused by people. Even if you strictly follow necessary safety procedures and precautions and believe you are safe, the incident might result due to someone else's unsafe or careless actions. Several incidents are reviewed, including personal injury and equipment damage by two experienced authors. [ABSTRACT FROM AUTHOR]

The subject of safety continues to be at the forefront of all forest products industry segments. However, a high frequency of serious electrical injuries and fatalities are still occurring around electrical equipment. Some of these events are attributed to the lack of proper regular routine maintenance practices. These events also result in high monetary losses associated with damaged property and production losses. This paper will outline some of the areas of concern and offer some perspective on how to plan better and schedule appropriate preventive maintenance. [ABSTRACT FROM AUTHOR]

This article explores the need for high-voltage arc flash (HVAF) assessment for utility workers who are exposed to the line to line voltages above 15 kV. The regulatory requirements will be discussed including OSHA, NESC, etc., to get an understanding of how utilities consider HVAF. Furthermore, the methods for evaluating HVAF, key driving factors, and rule of thumbs, and HVAF personal protective equipment will be discussed and compared in great detail to aid in the selection of a thermal incident energy evaluation method. The article includes an example application of HVAF assessment using various commercially available software. This example illustrates the importance of performing an HVAF assessment for utility applications and highlights the differences between thermal incident energy evaluation methods and how they can be conservatively applied for situations outside their intended application range. [ABSTRACT FROM AUTHOR]

Existing arc flash standards like IEEE 1584 and 1584.1 present models that can be used to estimate incident energy levels in power distribution equipment but provide limited direction regarding how equipment construction should be considered in the calculations. Users performing arc flash risk assessments are left to apply engineering judgment when considering how barriers or isolation of components should be considered. This can lead to risk assessments that are inconsistent or incorrect. Current practices regarding arc flash evaluation in barriered and nonbarriered equipment are reviewed based on current standards. Gaps and potential concerns are discussed, including the lack of defined criteria to use in calculations, along with lack of criteria for determining when barrier systems are considered effective at preventing, mitigating, controlling, or containing arcing faults. A description of a new system that provides passive protection in low-voltage distribution equipment is presented. By providing improved protection for the incoming conductors and main circuit breaker itself, this line-side protection system reduces or eliminates the uncertainties, which allows for more consistent and accurate application of risk assessments. The new protection system enables arc flash protection to be provided by a passive, enclosed system that has been tested to verify performance. As such, the calculations and risk assessment are less reliant on assumptions regarding the performance of the equipment. Practical aspects of arc flash analysis and labeling and operation and maintenance of such equipment are also discussed. [ABSTRACT FROM AUTHOR]

The interconnection between diverse Distribution Generations (DGs) that utilize various technologies and complex structure of networks are the most characteristic of modern Distribution Networks (DN). The wide adoption of DGs considerably affects the power flow dynamics in the DN and consequently the fault characteristics. The excessive level of fault currents can pose risks of heat (high temperature) and pressure in accordance to Arc Flash (AF) incident energy in microgrids. This research studies the relationship between AF severity and the solving of coordination problem of Overcurrent Relays (OCRs) in DN, and introduces a novel equation that considers the AF qualities in solving the coordination problem for OCRs. In this study, a novel optimization problem, the AF severity with the optimal coordination of OCRs in DN is presented and the Water Cycle Optimization Method (WCOM) is employed to find the best combination of the OCR’s settings in the DN while considering the AF induced energy. The proposed optimization approach and the novel equation are evaluated with an IEC microgrid and compared with the conventional protection method and Particle Swarm Optimization (PSO) used in optimizing the coordination of OCR in the DN. The optimal settings of the OCR scheme are achieved and examined on the modified IEC microgrid benchmark system. In order to verify the result, an industrial simulation package (ETAP) and OCR (GE Multiin, model-750/760) was used in this work.

Injuries sustained while performing electrical work are a significant threat to the health and safety of workers and occur frequently. In some jurisdictions, non-fatal serious incidents have increased in recent years. Although significant work has been carried out on electrical safety from a human factor perspective, reviews of this literature are sparse. Thus, the purpose of this review is to collate and summarize human factors implicated in electrical safety events. Articles were collected from three databases (Scopus, Web of Science, and Google Scholar), using the search terms: safety, electri*, human factors, and arc flash. Titles and abstracts were screened, full-text reviews were conducted, and 18 articles were included in the final review. Quality checks were undertaken using the Mixed Methods Appraisal Tool and the Critical Appraisal Skills Program. Environmental, individual, team, organizational, and macro factors were identified in the literature as factors which shape frontline electrical worker behavior, highlighting the complexity of injury prevention. The key contributions of this paper include: (1) a holistic and integrated summary of human factors implicated in electrical safety events, (2) the application of an established theoretical model to explain dynamic forces implicated in electrical safety incidents, and (3) several practical implications and recommendations to improve electrical safety. It is recommended that this framework is used to develop and test future interventions at the individual, team, organizational, and regulator level to mitigate risk and create meaningful and sustainable change in the electrical safety space.

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]

The electrical safety community has made great strides in reducing electrical injuries to electrical workers through elimination, mitigation, administrative controls, worker training, and personal protective equipment. However, a large percentage of fatal and nonfatal electrical injuries occur to nonelectrical workers. This article uses Bureau of Labor Statistics data and Occupational Safety and Health Administration records to identify workers and types of work vulnerable to electrical injury. Odds of electrical or occupational injury or fatality are included for risk perspective. To decrease the likelihood of electrical injuries in at-risk workers, electrical safety programs must effectively target and reach at-risk workers. Appropriate training and ways to reach nonelectrical workers vulnerable to electrical injury are discussed. [ABSTRACT FROM AUTHOR]

This paper reviews approaches used to detect and identify arcing currents, including arcing current faults. The reviewed approaches are categorized as the time-domain, frequency-domain, and time–frequency approaches. The time-domain approach extracts shoulders (zero values of the current around zero crossing points), spikes and jumps, abnormal magnitudes (lower or higher than normal), and high rate of change of the current. The frequency-domain approach extracts the high-frequency components, harmonic components, sub-harmonic components, and cross-correlation indicator. The time–frequency approach extracts high-frequency sub-bands that contain non-stationary frequency components, which may have non-stationary phases. The three approaches are implemented to test their accuracy, computational requirements, and sensitivity to system parameters. These tests are performed by processing of currents that are collected for normal and dynamic conditions, conventional faults, and currents with high or low arcing components. Test results provide a performance comparison for the tested approaches. [ABSTRACT FROM AUTHOR]

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]

With the emergence of dense power due to the use of relatively low-voltage infrastructures, which are becoming more common in distribution networks, the risks related to low-voltage arc flash are drawing more attention. Arc voltage, as the critical factor in arc flash mitigation, is strongly related to the determination of insulation distance and re-striking voltage level. However, while much attention has focused on the need for hazards calculation and the selection of appropriate personal protective equipment, the physical characteristics of arc has received relatively little attention. Although some related researches have been carried out in high-voltage arc faults with long gaps, the medium–low arc faults, which have more dynamic nature, is rarely to be investigated. To comprehensively analyze the voltage characteristics of medium–low-voltage arc fault in short gaps, this paper discussed the mathematical approach for arc voltage modeling. To achieve the reliable model parameters, the magnetohydrodynamic simulation method is explored as the amendment for mathematical model. Moreover, in order to have an easy application for on-site practice, a concisely alternative model for arc voltage gradient calculation is developed. The fitting result shows the model has a good ability to accurately estimate the voltage gradient of medium–low-voltage short arc. [ABSTRACT FROM AUTHOR]

High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse due to the limited fault current values and the situation is worse in wind farms. The mostly adopted HIF detection algorithms are based on the 3rd harmonic characteristic of the fault zero-sequence currents, whereas these 3rd harmonics are very easy to be polluted by wind power back-to-back converters. In response to this problem, the typical harmonic characteristic of HIF arc flash based on Mayr's arc model is first analyzed, and the typical fault waveforms of HIF in wind farm are presented. Then the performance of the harmonic based HIF detection algorithm is discussed, and a novel detection algorithm is proposed from the viewpoint of time domain, focusing on the convex and concave characteristic of zero-sequence current at zero-crossing points. A HIFs detection (HIFD) prototype implementing the proposed algorithm has been developed. The sensitivity and security of the algorithm are proved by field data and RTDS experiments.

High-impedance fault detection (HIFD) is crucial in an effectively grounded distribution system because of the potential threat of fire and electric shock. HIFD has been extensively researched for more than 30 years, and a harmonic component in zero-sequence current is typically used in detection algorithms since waveform distortion is often produced by arc flash. For a stable HIF, it would be invalid or has lower sensitivity because of the limited harmonic content in zero-sequence current waveform. To overcome this problem, in this paper, a novel detection algorithm is proposed for detecting waveform distortion in the time domain. First, for the analysis of arc flash, the solid dielectric electrical breakdown theory is verified to be more suitable than theories based on the heat accumulation theory, and a nonlinear arc model that can be used for analyzing arc flash is then proposed. Furthermore, a novel HIFD algorithm based on the identification of nonlinear voltage–current characteristic profiles (VCCPs) is proposed, with the focus on the quenching and restrike dynamic process of an arc flash. The high performance of the algorithm is verified by performing various simulations and examining field data. An HIFD prototype using the proposed algorithm was developed, and it showed excellent performance in real-time digital simulator tests. The VCCP based disturbance detection approach could also be popularized in the applications of relay protection, harmonic source location and early fault alarming in smart grid. [ABSTRACT FROM AUTHOR]

Arc Flash in low-voltage equipment (480 volts ac and below) is a safety issue that can impact work practices for electrical workers. When estimating incident energy for low-voltage equipment, the duration of the arc is typically the driving factor. This paper summarizes previous testing results that establish arc sustainability for various equipment configurations when trip devices do not operate. In some cases, arc duration is limited by the physical conditions of the enclosure and by the driving voltage and current available. Using the maximum duration for arc sustainability can provide more realistic estimated incident energies than using the 2 s self-extraction time cited in IEEE 1584–2002. Consequently, required levels of personal protective equipment can be reduced while still providing adequate protection to the worker. [ABSTRACT FROM PUBLISHER]

Arc-resistant low/medium-voltage switchgear and motor controls continue to provide proven levels of additional personnel safety in most every petroleum and chemical facility. The IEEE and the International Electrotechnical Commission generated testing guides and standards for these products, which are open to some level of interpretation when applied to products other than traditional medium-voltage circuit breaker or fundamental motor controller structures for which the current available standards and guides were intended when they were initially written. All medium-voltage variable frequency drives, because of their inherent designs, require high volumes of cooling air, which pose a real challenge in regards to providing full arc-resistant capabilities and compliance to the present testing guides, procedures, and standards. This paper will deliver real solutions to this problem through the application of unique cooling processes, arc channeling technologies, structural enhancements, arc fault energy-limiting methodologies, and special application considerations when applying arc-resistant medium-voltage drives. [ABSTRACT FROM AUTHOR]