Arc Flash Hazard Analysis Research Articles

Book Reviews [7 books reviewed

The following seven books are reviewed: Condition Monitoring with Vibration Signals (Ahmed, H. and Nandi, A.K.; 2020); Ferroelectric Materials for Energy Harvesting and Storage (Maurya, D., et al; 2021); Arc Flash Hazard—Analysis and Mitigation, 2nd Edition (Das, J.C.; 2021); Metal Oxide Powder Technologies— Fundamentals, Processing Methods and Applications (Al-Douri, Y.; 2021); Thermodynamics— Principles and Applications, 2nd Edition (Tosun, I.; 2020); Compendium on Electromagnetic Analysis— From Electrostatics to Photonics: Fundamentals and Applications for Physicists and Engineers, 5 Vol. Set (Donahue, M., et al; 2020); and Principles of Dielectric Logging Theory (Kaufman, A. and Donadille, J.; 2021.

Investigation of Arc Flash in Single-Phase Vertical Conductors in a Box

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.

DC Arc Flash Studies for Solar Photovoltaic Systems: Challenges and Recommendations

A dc arc flash hazard exists in solar photovoltaic (PV) power systems, but there is no widely accepted methodology for characterizing the severity of the hazard. Calculation methods have been proposed, and most rely on the nameplate $I$ – $V$ characteristic of the PV modules at standard test conditions to determine the worst case incident energy. This paper proposes to consider other factors in performing a dc arc flash hazard analysis, including possible weather conditions and variations of PV module characteristics from the datasheet ratings. It is recommended to consider two conditions when determining the worst case incident energy from a PV system: 1) the failure of all protective devices to trip within 2 s due to insufficient current and 2) the array output power exceeding the nameplate rating due to technological and environmental factors.

Arc-Flash Hazard Calculations in LV and MV DC Systems—Part I: Short-Circuit Calculations

The IEEE 1584 Guide does not address arc-flash hazard in dc systems. The interest in this subject is evidenced by current publications. The National Fire Protection Association (NFPA) 2012 methodology has added a small description of the calculations of arc-flash hazard in dc systems. However, there are serious inaccuracies in the application of the methodology that is advocated in the NFPA. A review of the current literature indicates that there is no comprehensive document on the subject and that some of the assumptions made in the current literature are not accurate, e.g., with respect to the short-circuit current profiles and protective devices in dc systems, which are very fundamental to the accurate calculations of arc-flash hazard in dc systems. This paper is presented in two parts. This part provides equations with practical examples of short-circuit calculations in dc systems. The second part provides the analysis of arc-flash hazard. Accurate calculations of the short-circuit currents and ascertaining their profiles is the first step in the arc-flash hazard analysis.

Make the Connection: Relating Electrical-Safety Maintenance to Reliability

The results of electric-shock and arc-flash hazard and risk analysis are dependent on certain aspects of the electrical equipment to be maintained, including the mechanical integrity of covers, doors and barriers, the mechanical and electrical integrity of bonding and grounding systems, and the functional performance of circuit-protection devices and protection systems. In addition, the frequency of personnel exposure associated with maintenance tasks is dependent on the effectiveness of the reliability and maintenance programs in place. This article introduces two concepts to help differentiate maintenance strategies: electrical-safety-critical maintenance and electrical-safety-dependent maintenance.

Investigation of Factors Affecting the Sustainability of Arcs Below 250 V

Recent testing with various electrode configurations and insulating barriers suggests that 250-V equipment omitted from arc flash hazard analyses has the potential for burn injury. Research into the sustainability of arcs at these voltages shows that assumptions about the magnitude of these hazards need to be revised. This research enhanced the work of previous efforts by focusing on the sustainability of arcs with fault currents lower than 10 kA. Gap lengths between electrodes, electrode shape, electrode material, and voltage variations are studied for their effects on arc sustainability. A modified barrier design representative of the space around panelboard bus bars is also studied.

Understanding and Quantifying Arc Flash Hazards in the Mining Industry

Arc flash generally refers to the dangerous exposure to thermal energy released by an arcing fault on an electrical power system, and in recent years, arc flash hazards have become a prominent safety issue in many industries. This problem, however, has not been effectively addressed in the mining industry. Mine Safety and Health Administration (MSHA) data for the period 1990 through 2001 attribute 836 injuries to “noncontact electric arc burns,” making them the most common cause of electrical injury in mining. This paper presents results from several elements of a recent National Institute for Occupational Safety and Health study of arc flash hazards in mining and provides information and recommendations that can help reduce these injuries. The characteristics of past arc flash injuries in mining are first outlined, such as the electrical components and work activities involved (based on MSHA data). This is followed by a review of important concepts and terminology needed to understand this hazard. Next, methods for identifying, measuring, and managing arc flash hazards on a power system are covered, with emphasis on recommendations found in NFPA 70E, Standard for Electrical Safety in the Workplace. Finally, results are presented from a detailed arc flash hazard analysis performed on a sample mine electrical power system using IEEE 1584-2004a, focusing on components and locations presenting severe hazards, as well as engineering solutions for reducing the risk to personnel.

Modified Medium-Voltage Arc-Flash Incident Energy Calculation Method

The IEEE Standard 1584-2002 provides a guide for conducting arc-flash hazard analyses for low- and medium-voltage systems. Users, however, need to be aware that the models in the guide were based on the measurements of arc incident energy under a specific set of test conditions combined with theoretical work. In the medium-voltage arc-flash analysis, the incident energy calculation, according to the guide, is a function of system voltage, gap between conductors, the distance from the possible arcing point to the worker, the bolted three-phase fault, and the arc clearing time from the source-side protecting device. However, the effect of fault current decaying is not considered in the current guide. According to an IEEE-recommended short-circuit calculation method, the fault contributions from generators and induction and synchronous motors would usually decay over the short-circuit period based on their short-circuit time constants and the excitation system. Therefore, the standard calculated incident energy from short-circuit point of view would be higher than the value if the effect of decaying current were considered. On the other hand, the arc clearing time according to the current guide is derived from the initial bolted three-fault current, which would result in a shorter arc clearing time. As a result, the standard calculated incident energy value from arc clearing point of view would be lower than the value if the effect of decaying current were considered. Therefore, there are two conflicting elements contained in the current guide, which may result in an inconclusive personal protective equipment requirement. This paper will present a modified incident energy calculation method based on the decaying three-phase fault current and also based on the arc clearing time derived from decaying three-phase fault current at the time of fault interruption. A sample calculation and a comparison of the results of the current method and the modified method are presented in this paper.

Impact of Available Fault Current Variations on Arc-Flash Calculations

Prior to the arrival of the arc-flash hazard analysis and the incident energy calculations, it was common practice to perform short-circuit studies assuming an infinite source on the primary of the service transformer. With the main goal of a short-circuit study being to compare the maximum calculated short-circuit current to the short-circuit rating of protective devices, using an infinite source resulted in the most conservative short-circuit current. However, since the amount of energy available in an arc-flash incident is not only dependent on the available short-circuit current but also on the clearing time of the protective device, the assumption of an infinite source on the transformer primary will not guarantee the most conservative results for the incident energy calculations downstream of the transformer. This paper examines the effect of the utility available fault current on the incident energy calculations and proposes a new method to calculate the conservative arc-flash results in the event that the actual utility fault information is not available.

Power-System Protection in an Oil-Field Distribution System

Power-system protection for oil-field distribution systems consists of protection for electrical submersible pump (ESP) installations and their upstream electrical circuits. In this paper, a comprehensive protective-device coordination and an arc-flash hazard analysis are conducted for a large oil-field distribution system. Various protection schemes are investigated and compared. This paper focuses on three areas: ESP installation protection using switchboards, the protective-device coordination of upstream electrical circuits of ESP wells, and how to obtain the optimized protective-device settings for both protection and arc-flash-safety concerns. ESP installation protection using fuses is first addressed. ESP wells that cannot be protected by fuses are particularly investigated, and a motor controller used with a fuse can provide a better protection for such ESP wells. A motor control center (MCC) for two large water injection pumps is used as a case study for the protective-device coordination of upstream circuits of ESP wells. Nuisance tripping was experienced during a motor starting at a 1750-hp water injection pump. The investigation indicates that improper relay settings at the MCC were the root cause. The optimized protective-device settings can be achieved by conducting a protective-device-coordination study and an arc-flash hazard analysis by keeping both protection and arc safety in mind.

Arc-Flash Incident Energy Reduction Using Zone Selective Interlocking

As a result of new requirements in the National Fire Protection Association (NFPA) 70E standard, many facilities are performing arc-flash hazard analyses to better understand how to protect personnel from the possibility of being injured in an arc-flash incident. In many cases in the petrochemical industry, it is unsafe or not practical to shut down electrical equipment to do work. This paper explores practicable options that a facility has to reduce incident energy levels in existing low-voltage systems where the arc-flash hazard analysis results in unacceptably high levels. It also explores a case study in the Gulf of Mexico, where an offshore oil production platform was able to cost effectively reduce incident energy levels from approximately 170 to under 15 by implementing a zone selective interlocking system into their low-voltage switchgear. The selection process logic involving equipment, personnel considerations, and commissioning are all addressed.

Arc Flash and Coordination Study Conflict in an Older Industrial Plant

Once arc flash hazard analysis became a requirement for many industrial power system studies, the reduction of arc flash hazards has become an important concern. Inevitably, the factors that lead to reductions in arc flash hazards do not always lead to an improvement in other areas, i.e., in particular, protective device coordination. This paper will examine several particular cases where an arc flash hazard analysis of an older industrial plant yielded several cases of buses where the hazard level was ldquoextreme dangerrdquo above category 4. By changing protective device settings and, if necessary, the devices themselves, the hazard level can be reduced. Methods to maintain coordination, if possible, are discussed.

Impact of Arc Flash Hazards on Medium-Voltage Switchgear

This paper discusses the arc flash ramifications associated with the design and selection of medium-voltage switchgear. Three case studies are presented to demonstrate the impact of performing arc flash hazard analysis on the proposed and/or existing medium-voltage installation at the design stage. This paper proposes the following: 1) changes in the National Electrical Code, Article 110.16, to provide mandatory requirements for a) performing arc flash analysis at the design stage and b) placement of warning labels on switchgear to warn qualified persons of potential arc flash hazards and 2) a need to promulgate regulations requiring a utility company to notify its customers of changes in a) the available fault duty at the point of common coupling with a customer's facility and b) utility upstream protective device settings.

Current Methods for Conducting An Arc-Flash Hazard Analysis

With the advent of the 2000 edition of National Fire Protection Association (NFPA) 70E, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Standard</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">for</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Electrical</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Safety</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Requirements</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">for</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Employee</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Workplaces</i> , comes a new language addressing the threat of arc flash. While this threat has been around for many years, it has received considerable attention in recent years due to the necessity of working on energized equipment and the subsequent accidents involving arc flash each year. Included in NFPA 70E-2004 are terms such as flash hazard, flash-protection boundary, and incident energy. This paper will describe the three methods for conducting an arc-flash hazard assessment contained in NFPA 70E-2004, as well as the IEEE Std 1584-2002 method of conducting an arc-flash hazard analysis. This paper will discuss the effectiveness and merit of each technique. In addition, a sample system will be analyzed and used to compare the results of each hazard-assessment method.

A Practical Approach to Arc Flash Hazard Analysis and Reduction

Recent efforts to quantify the dangers associated with potential arc flash hazards rely on overcurrent protection to remove a given fault condition. The effectiveness of various devices is determined by a clearing time related to the maximum available fault current for each system location. As industrial and commercial facilities begin to embrace arc flash labeling procedures and begin to recognize arc flash prevention as a part of a complete safety program, the current method of calculation will allow them to quantify the incident energy (cal/cm/sup 2/) associated with a maximum three-phase fault condition. Most faults produce current magnitudes less than the three-phase maximum. This paper will consider fault current magnitudes less than that of the maximum three-phase condition, and discuss the resulting calculations for incident energy across the range of current magnitudes. Under these additional scenarios, the performance of various overcurrent protection devices will be demonstrated. Associated considerations for design, modeling, and maintenance will be presented.