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Electrical Safety, Electrical Hazards, and the 2018 NFPA 70E: Time to Update Annex K? Tammy Gammon, Senior Member, IEEE, Wei-Jen Lee, Fellow, IEEE, Zhenyuan Zhang, Student Member, IEEE, and Ben C. Johnson, Life Fellow, IEEE

Abstract—Sharing the same goals and overlapping membership, IEEE and NFPA are committed to improving electrical safety in the workplace. Knowledge about electrical hazards, particularly arc flash hazards, has expanded greatly since the first 2002 edition of the IEEE Standard 1584, IEEE Guide for Performing Arc-Flash Hazard Calculations. In the NFPA 70E Standard, 2004 edition, the 1584 arc-flash hazard calculations were included in the recommended methods for quantifying the potential incident energy exposure. In 2004, IEEE and NFPA initiated the IEEE/NFPA Arc Flash Collaboration Project to conduct research and testing which would lead to a greater scientific understanding of the arc flash hazard. Presently, IEEE Standard 1584 is in the process of major revision. Subsequent editions of NFPA 70E— the 2009, 2012 and 2015—have greatly expanded the coverage of the arc flash hazard. However, NFPA 70E Annex K, which addresses the general categories of electrical hazards, has changed little since the 2004 edition, except for the addition of a short paragraph on arc blast hazards in 2009. This paper suggests content for expanding the 2018 NFPA 70E Annex K. Index Terms—Arc flash, electrical hazard, electrical safety, electrical shock, NFPA 70E.

I. I NTRODUCTION

T

HE first edition of NFPA 70E, entitled Standard for Electrical Safety Requirements for Employee Workplaces, was published in 1979 to help OSHA provide guidance on electrical safety in the workplace. In 2004, NFPA 70E, retitled Electrical Safety in the Workplace, first included annexes to provide supplementary information so that the requirements of 70E might be better understood and implemented with greater ease. Since the 2004 70E edition, the number of annexes and the depth and range of their content on achieving electrically safe work places have increased significantly. However, NFPA 70E’s 2015 Annex K, General Categories of Electrical Hazards, is very sim-

Manuscript received February 3, 2014; revised June 10, 2014 and January 20, 2015; accepted January 22, 2015. Date of publication February 24, 2015; date of current version July 15, 2015. Paper 2014-CSC-0017.R2, presented at the 2014 IEEE Industrial and Commercial Power Systems Technical Conference, Fort Worth, TX, USA, May 20–23, and approved for publication in the IEEE T RANSACTIONS ON I NDUSTRY A PPLICATIONS by the Codes and Standards Committee of the IEEE Industry Applications Society. T. Gammon is with John Matthews & Associates, Cookeville, TN 38502 USA (e-mail: [email protected]). W.-J. Lee and Z. Zhang are with The University of Texas at Arlington, Arlington, TX 76019 USA (e-mail: [email protected]; zhenyuan.zhang@mavs. uta.edu). B. C. Johnson is with Thermon Manufacturing Company, San Marcos, TX 78666 USA (e-mail: [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIA.2015.2406852

ilar to the original Annex K printed in 2004. The only additional Annex K material, added in 2009, is a short section on arc blast. NFPA 70E focuses on establishing a safe workplace for employees involved with the installation, troubleshooting and maintenance of electrical equipment. Moreover, the purpose of 70E as defined in Section 90.1 is “to provide a practical safe working area for employees relative to the hazards arising from the use of electricity [1].” Understanding the nature and consequences of electrical hazards provides the impetus for developing and following electrically safe work practices. Over the last decade, considerable effort has been expended in redeveloping 70E with the goal of establishing safer work environments. Annex K should convince employers how critical electrical safety programs are. Annex K should also convince workers how critical it is to follow safe work practices and to be able to recognize unsafe electrical conditions. For the maximum effectiveness of 70E, redevelopment and expansion of Annex K needs consideration in three areas. Annex K should identify 1) the range of electrical hazards; 2) the threshold electrical parameters capable of causing various physiological responses and injury from electrical shock; and 3) the types of potential injury and the physical mechanisms (as well as thresholds) such as heat, light and pressure capable of human harm during an arcing event. The NFPA 70E-2015 Annex K is reprinted in its entirety in this introduction for easy comparison and review with additional content suggestions which appear in subsequent sections of this paper. Suggested content for Sections K.1 and K.2 are provided in Sections II and III. The 70E-2015 Sections K.3 and K.4 should be combined to address all hazards associated with an arc-flash explosion; suggested content is provided in Section IV. The suggested Annex K content will need to be rewritten and presented in a manner which best engages all members of the electrical safety community, including managers, workers, contractors and inspectors. The prose injury descriptions presented in this work and thresholds may need to be presented in “easy access” table or graphical form for quicker comprehension. Other than citation numbers, less substantiation will be provided about the reference information and statistics. The reproduction of Annex K also serves another purpose. NFPA 70E has been widely cited for its informative and injury data. However, NFPA did not generate this data, and not all material and statistics have been adequately documented. NFPA 70E is viewed as a worldwide authority on electrical hazards and electrical safety in the workplace. It is critical that it reflects

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the most authoritative, published scientific work. The suggested content for Annex K in Sections II–IV is well referenced. This paper also serves as a concise summary, capturing the critical details of the publications and studies cited. Informative Annex K. General Categories of Electrical Hazards, NFPA 70E-2015: [Reproduced with permission from NFPA70E-2015, Electrical Safety in the Workplace, Copyright 2014, National Fire Protection Association. This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety. Electrical Safety in the Workplace and NFPA70E are registered trademarks of the National Fire Protection Association, Quincy, MA.] K.1 General Categories: There are three general categories of electrical hazards: electrical shock, arc flash, and arc blast. K.2 Electric Shock: Approximately 30 000 nonfatal electrical shock accidents occur each year. The National Safety Council estimates that about 1000 fatalities each year are due to electrocution, more than half of them while servicing energized systems of less than 600 V. Electrocution is the fourth leading cause of industrial fatalities, after traffic, homicide, and construction accidents. The current required to light a 71/2-W, 120-V lamp, if passed across the chest, is enough to cause a fatality. The most damaging paths through the body are through the lungs, heart, and brain. K.3 Arc Flash: When an electric current passes through air between ungrounded conductors or between ungrounded conductors and grounded conductors, the temperatures can reach 35 000 ◦ F. Exposure to these extreme temperatures both burns the skin directly and causes ignition of clothing, which adds to the burn injury. The majority of hospital admissions due to electrical accidents are from arc flash burns, not from shocks. Each year more than 2000 people are admitted to burn centers with severe arc flash burns. Arc flashes can and do kill at distances of 3 m (10 ft). K.4 Arc Blast: The tremendous temperatures of the arc cause the explosive expansion of both the surrounding air and the metal in the arc path. For example, copper expands by a factor of 67 000 times when it turns from a solid to a vapor. The danger associated with this expansion is one of high pressures, sound, and shrapnel. The high pressures can easily exceed hundreds or even thousands of pounds per square foot, knocking workers off ladders, rupturing eardrums, and collapsing lungs. The sounds associated with these pressures can exceed 160 dB. Finally, material and molten metal are expelled away from the arc at speeds exceeding 1120 km/hr (700 mi/h), fast enough for shrapnel to completely penetrate the human body. II. S UGGESTED C ONTENT FOR K.1 K.1 E LECTRICAL H AZARDS Both electrical shocks and arc-flash explosions represent electrical hazards in the workplace. Although the electric utility industry is often associated with electrical hazards, potential electrical hazards are present in all workplaces. According to the U.S. Bureau of Labor Statistics (BLS), 1635 electrical fatalities occurred in the private sector between 2003 and 2010; however, 52% occurred in the construction industry alone and

TABLE I 2003–2010 N ONFATAL E LECTRICAL I NJURIES , P RIVATE I NDUSTRY∗

only a total of 11% occurred in the trade, transportation and utilities industries [2]. Electrical fatalities accounted for 10.4% of the industrial fatalities after motor vehicles and violence, the leading causes of industrial fatalities, were eliminated from the list. Non-fatal electrical injuries accounted for 8.7% of the total nonfatal injuries which occurred in the private sector. As Table I shows, the utilities industries account for only a small number of the 20 350 nonfatal electrical injuries that occurred in the same time period. The numbers of shock and burn injuries and fatalities are probably higher than the BLS statistics indicate. Many less serious incidents were probably not reported. Furthermore, since electrical injuries are defined by the category “contact with electric current,” it is likely that a number of arc flash injuries were miscategorized. Tragic electrical incidents may also cause extensive injuries which result in death after the required reporting period for fatalities has elapsed. According to statistics compiled by CapSchell [3], five to ten arc flash explosions occur every day and result in ten to fifteen employees being hospitalized and one to two dying as a result of burn injuries. The 2003–2010 BLS data presented in [2] suggests an average of 205 electrical fatalities and 2544 electrical injuries occur each year. The CapSchell statistics indicate that 365 to 730 electrical fatalities and 3650 to 5110 nonfatal electrical injuries occur from arc-flash explosions alone, not including those from electrical contact accidents. III. S UGGESTED C ONTENT FOR K.2 K.2 E LECTRICAL S HOCK1 Table II lists thresholds for 60-Hz, 10 000-Hz and dc electric shock currents established from Dalziel’s early research involving human and animal experiments. An individual’s response to shock current depends on weight, height, bone structure, and muscular development [4], [5]. Shock thresholds for dc and higher frequency ac systems are higher than those for 50/60-Hz power systems. Fig. 1 illustrates that shock current thresholds for ac systems generally increase as a function of frequency, particularly above 1000 Hz. Table III provides current thresholds listed in IEC TS 60479-1. The thresholds of ventricular fibrillation for 1- and 3-s shocks are based on electrical accident data and represent a lower boundary of a time-current plot [6, Fig. 20]. For short shock duration periods less than 0.1 s, ventricular fibrillation is likely to occur only during the vulnerable period of the heart cycle. 1 Note: Unless explicitly indicated as in Fig. 1 and Tables II–IV, the voltage and current levels discussed in Section II apply to 50/60-Hz, ac power systems.

GAMMON et al.: ELECTRICAL SAFETY, HAZARDS, AND THE 2018 NFPA 70E, TIME TO UPDATE ANNEX K?

TABLE II C URRENT T HRESHOLDS D ETERMINED IN DALZIEL’ S E ARLY R ESEARCH [4]

Fig. 1. Dalziel’s research: Let-go current versus frequency [4] 1956 IEEE. Reprinted with permission from C. Dalziel [4]. TABLE III C URRENT T HRESHOLDS IN S TANDARD IEC TS 60479-1 [6]

Even an extremely low-level shock causing a startle reaction (an uncontrolled muscular reaction) has a potential for injury, if it causes a response such as tripping or falling. The threshold startle reaction for an adult is 0.5 mA, the maximum level

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of allowable current leakage from an appliance permitted for most circumstances. Shock current becomes dangerous (as well as extremely painful) at the “let-go” current, the current level that causes the hand to involuntarily close and grasp on a conductor. The “inability to let go” threshold for an adult has been set at 6 mA, higher than the 5-mA trip level required for GFCI devices [7]. When a person cannot “let go,” perspiration increases and skin resistance decreases, so higher levels of current flow through the body. Respiratory paralysis, the loss of voluntary control over the respiratory muscles, can be fatal at current levels of 30 mA for a 68-kg (150-lb) adult [8]–[10]. Electrical workers standing on ladders have broken free from low-voltage2 “let-go” shocks by kicking the ladder away from themselves and falling. The response to let-go currents at high voltage can differ significantly: a person’s grasp of a conductor may involuntarily tighten, or the person may be propelled from the conductor [5]. By definition, electrocution is death caused by electrical shock. Electrocution sometimes occurs from respiratory arrest, current flow though the respiratory center in the brain; however, current flow through the heart is usually the cause of electrocution. The heart muscle stops pumping blood either due to cardiac asystole or ventricular fibrillation. Cardiac asystole is the stopping of the heart; asystole occurs from contact with high voltage which generate shock currents greater than 1 A in the body [12], [13]. Cardiac asystole does not necessarily lead to death, since a fall or blow to the chest may cause the heart to revert to a normal rhythm without medical defibrillation. Ventricular fibrillation is the most common cause of electrocution, particularly for voltages below 1000 V. Based on 0.5% of 70-kg (154-lb) adults, the fibrillation threshold is commonly set at 100 mA for a 3-s shock duration [14], [15], but has been associated with currents as low as 30 to 50 mA in the literature [16]. When a human heart enters a state of ventricular fibrillation, which is a rapid, uncoordinated and asynchronous quivering of the heart, it rarely reverts to a normal heart rhythm without medical defibrillation. Particularly at low voltages such as 120 V, death can occur without any electrical burns on the body and without any conclusive autopsy findings. People with heart conditions, may be susceptible to ventricular fibrillation at thresholds below the normal population. Early literature reports “a number” of electrocutions occurring from 65-V circuits and even one from 46 V [17]. More recently seven cases of electrocution, four occurring at 24 to 75 Vac and three at 36 to 75 Vdc have been reviewed in [18]. The severity of a shock is determined by the magnitude, the duration and the path of current flow through the body. Ohm’s law is commonly used to estimate the shock current as the quotient of the contact voltage and 500 ohms, the initial, internal resistance based on 5% of the population [6]. This conservative estimate excludes skin resistance. The body impedance is actually a nonlinear function of current path and

2 The term “low-voltage” refers to system voltages up to 600 V. The National Electric Code [11] considers voltage over 600 V, “high voltage.” The descriptive term, “high voltage” in Section III most aptly refers to all “medium voltage,” distribution and transmission systems associated with voltages of 2400 V and higher.

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TABLE IV T OTAL B ODY I MPEDANCE (Ω) NOT E XCEEDED IN 50% A DULTS , H AND - TO -H AND C ONTACT [6]

duration, touch voltage, skin moisture, contact pressure, and contact surface area. In Table IV, the total body impedance (50% of the population) for hand-to-hand contact is provided for several touch voltages at different moisture levels and contact surface areas. As the touch voltage increases to 700 V, the total body impedance asymptotically approaches the internal body impedance. A person lying on the ground with a defective tool on his chest might have a much lower internal body resistance, on the order of 100 Ω [13]. In longer duration shocks after the skin has broken down, the total body impedance approaches the internal body impedance for touch voltages over about 100 V [6]. Blisters have been known to form (and the skin’s resistance drops) after human skin had made contact with a 50-V energized circuit for 6 or 7 s [17]. The skin resistance is inherently low at the location of a cut or abrasion. Dalziel [19] reported, “At 240 V and above, the voltage punctures the skin instantly, leaving a deep localized burn.” When the skin’s protective barrier breaks down, a person is at much greater risk for serious electrical shock injury. In high-voltage contact accidents, the injured worker usually has skin destruction at the contact points, but any involved extremities may only be slightly swollen. However, the skeletal muscle in the affected extremity is in “a state of severe unrelenting muscle spasm or rigor,” and frequently has “marked sensory and motor nerve malfunction [20].” Nerve damage and poor circulation cause the limb to be weak, stiff and cold; “the patient is often served by amputation of the damaged extremity and replacement with a functional prosthetic extremity [20].” Amputation rates as high as 65% have been noted in highvoltage contact accidents [21]. Experienced physicians have compared electrical trauma to crush injuries because both types of injuries are characterized by the “relative vulnerability of the nerve and muscle tissues,” as well as the large release of intracellular contents from the damaged skeletal muscle into the circulating blood. The release of large protein molecules can result in kidney failure. The release of ions can significantly shift blood serum concentrations, affecting the heart and other organs [20]. Electrical shock injury can be very complex. Nerve damage may occur from even brief shocks without an appearance of muscle injury [20]. Some immediate effects of electrical shock can include confusion, headache, amnesia and unconsciousness. Secondary effects lasting on the order of hours to days can include paralysis in the legs, muscular pain, vision abnormality, swelling, headache and cardiac irregularities. Long range effects may not surface for several years and may

include paralysis, speech or writing impairment, loss of taste, and numerous other disorders resulting from damage to the nerve tissues, which do not regenerate [22]. In recent years, a type of electrical shock injury, identified as “diffuse electrical injury” has resulted in the development of chronic physical and neuropsychological issues from low-level electrical shocks that were not expected to cause long-term injury. Common physical symptoms include muscle aches, generalized fatigue, numbness and path related weakness and tingling. Common neuropsychological symptoms include insomnia, increased anxiety, concentration and cognitive problems, personality changes, and short term memory loss [23], [24]. IV. S UGGESTED C ONTENT FOR K.3 K.3 A RC -F LASH E XPLOSION When an arcing fault occurs, an unintended current path (between phases or phase and ground) forms directly through air. An “arc-flash” incident is characterized by a flash of bright light, and is often accompanied by loud boom. Often an arcflash incident is truly an explosion, associated with the generation of energy and release of high-temperature gases [25]. Arc temperatures can reach 20 000 K (35 000 ◦ F) [26]. A person standing two feet from a 25 000-A arc might experience a blast pressure of 160 lb/ft2 (1.1 psi) [27]. In the vast majority of arc incidents, thermal burn injuries cause the greatest harm. A. Thermal Energy/Burn Injury The level of burn injury depends on many parameters, including the magnitude of the fault current, a person’s distance to the arc, and the duration of the fault. (Note: Burn injury may be prevented with appropriate PPE!) For a short-duration arc, the generated heat may cause superficial flash burns to exposed skin, such as the face, neck, and hands [28]. The rapid generation of heat may even carbonize the skin without the development of deep injury [29]. However, the ignition of clothing gives rise to deeper, more serious burns. Fig. 2 illustrates that a person’s chance of surviving a serious burn injury is a function of age and the percentage of the total body surface area burned. Surviving serious burn injury also depends on the depth and location of the burns. Other survival factors include preexisting health conditions (such as cardiac, liver, or lung disease) and secondary burn effects (such as circulatory shock and pulmonary edema). If a victim survives the initial period of shock, death may occur in the following weeks due to the secondary effects on the brain, heart, lungs, liver, and kidneys [30]. Irreversible burn damage has been hypothesized to occur when the skin reaches a temperature of 96 ◦ C (205 ◦ F) for 0.1 s [26] (based on earlier work [30]–[32]). Although this prediction is conservative because the local cooling effects of blood circulation have been neglected, it is quite low compared with Table V, temperatures recorded from thermocouples on a mannequin during a staged arc test. The “safe” threshold for incident heat on bare skin has generally been accepted at 1.2 cal/cm2 [35], based on Stoll’s onset of a 2nd degree burn, which involves the formation of a blister [36]. Fabric testing on blue cotton, twill shirt material,

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TABLE VI P RESSURE T HRESHOLDS [43]

TABLE VII P RESSURES R ECORDED F ROM A RC T ESTS

Fig. 2. Burn survival: function of age and body percentage burned (Data source: 2002–2011 National Burn Repository data [33]). TABLE V T EMPERATURES ON M ANNEQUIN ’ S E XTENDED H AND AND N ECK [34]∗

5.2 ounces per square yard, demonstrated a 90% chance of ignition when exposed to incident heat levels of 6.9 cal/cm2 [37]. The arc rating of personal protective equipment (PPE) is the energy level incident on the equipment that has a 50% probability of: 1) transferring 1.2 cal/cm2 to a surface (i.e., person) under the PPE (ATPV) or; 2) the fabric breaking open (EBT). Workers can experience serious burn injuries if the incident energy rating of the PPE is less than the incident heat experienced during an arc-flash incident. B. Pressure/Blast Injuries When an arcing fault is initiated, a high-pressure front is created as the expanding gases in the vicinity of the arc compress the surrounding air. The blast wave from general explosions travels outward at supersonic speeds that may exceed 900 mi/h (463 m/s) [38]. The severity of the blast pressure depends on the initial peak pressure, the duration of the overpressure, a person’s distance from the explosion, and “the degree of focusing due to a confined area or walls [39].” Blast pressures are greater when the explosion occurs indoors, particularly in small enclosed rooms (such as electrical closets), and the pressure wave reflects from the walls [40]. A worker may actually be far enough away from the arc to escape burn injury, but sustain severe blast injury to due to the propagation of the pressure wave in the room [41]. Primary blast injuries directly result from the pressure wave striking the air- and fluid-filled organs. Primary blast injuries can cause collapsed lungs, ruptured eardrums, or concussions without a direct blow to the head [42]. In a worker who appears unharmed immediately after an arc-flash explosion, loss of hearing (which may be temporary or permanent), confusion, and unsteady walking may indicate a blast injury. Other symptoms such as concentration difficulty, depression, and memory problems may not surface for weeks after the arc-flash explosion [41], [43]. Various pressure thresholds associated with

pressure injury, along with the OSHA limit for impulsive noise, are listed in Table VI. For comparison, Table VII contains some limited pressure data from arc tests. Pressure measurements taken in closed equipment demonstrate a huge potential arcblast hazard. Secondary injuries result from flying debris propelled by the blast wind. Wounds can occur anywhere, including the eye and head. During an arc-flash explosion, flying molten material may cause direct burn injury to the skin or ignite clothing. People can also be injured by shrapnel or projectiles. Shrapnel refers to all types of high-velocity fragments resulting from an explosion [44]. Any object [45], including bolts, tools, and even heavy equipment, can become a projectile in an arc-flash explosion. The threat of shrapnel is linked to the magnitude of the blast pressure. Shrapnel tends to be irregular in shape and has sharp edges. The velocity of shrapnel during an arc blast is “generally considered to start at approximately 150 to 180 m/s (500–600 ft/s) [46].” Arc-flash hood windows and face shields must meet the projectile impact requirements of ANSI Z87, which specifies that a 6.4-mm steel ball must not penetrate at a velocity of 91.4 m/s (300 ft/s). The ballistics test performance of two hood shield windows and two arc flash suits to 5.6-mm, nonspherical fragments appears in Table VIII. Tertiary blast injuries result from individuals being thrown by the blast. During an arc-flash explosion, individuals may be injured by being thrown off a ladder or propelled into a wall or equipment. But the tertiary effects of the arc blast may also help reduce the severity of burn injury. C. Light/Eye Injury Very brief, arc-flash incidents sometimes occur without causing burn or blast injury to nearby workers. However, the bright

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TABLE VIII BALLASTIC R ESULTS : 50% OF F RAGMENTS P ENETRATING S PECIMEN [46]

TABLE X N ON -B URN I NJURIES F ROM OSHA “E LECTRIC A RC ” R ECORDS [55],[56]

TABLE IX L IGHT L EVEL M EASUREMENTS IN R ECENT P UBLICATIONS TABLE XI OSHA “E LECTRIC A RC ” AND “B URN ” R ECORD I NJURIES (1984–2007) [58]∗

light, visible within a millisecond, may cause flash blindness. (Limited light data from two arc tests is listed in Table IX.) flash blindness is a temporary vision loss, which occurs when the retina receives excess thermal energy, but not enough to cause a burn. A reduction in visual acuity can last a few minutes or a few days. The recovery time from flash blindness depends on the brightness, size, and direction of the light flash, as well of the light spectrum and person’s age [50]. Recovery times also increase when a pupil is more dilated [51], as in the case of a person’s pupil size increasing to receive more light in a dimmer environment. Light radiated by an arc flash covers part of the ultraviolet region, predominately in the range of 200 to 600 nm [52]. Long term visual effects from ultraviolet and infrared light exposure may also occur. Cataract development is fairly common in workers surviving significant injuries from arc-flash explosions [41]. Testing has indicated that safety glass significantly reduced the energy reaching the eye to about 40% [37]. D. OSHA Arc Flash Records OSHA arc flash records have been analyzed to substantiate the reality of nonthermal burn injuries and to correlate burn injuries and fatalities with voltage level. An analysis of 424 public OSHA records from 1980 to 2004 involved investigations on electric arc injuries and fatalities3 ; nonthermal injuries were reported in 7.3% of the records. It was noted, “The risk of burn injuries from this hazard can be very severe. However, an elec3 For reference information only: According to the Occupational Health and Safety Standard, 29 CFR 1904.39, a work-related accident resulting in a death (within 30 days of the incident) or the hospitalization of three or more employees must be reported to OSHA [54]. In 2005, David Wallis presented an analysis of 454 public records of OSHA investigations involving electric arcs which occurred between 1980 and 2004; 30 incidents, involving arc welders, arc furnaces, and electric shock, were eliminated. A subsequent analysis was conducted on 2005–2008 OSHA records. Five of the 100 “electric arc” records were eliminated on similar grounds. In the 2005–2008 data, the four records of eye injuries were: two flash burns to the eyes (with no face injury specified), momentary blindness, and required eye flushing from a fault causing a battery to blow up in a person’s face. An additional record, not included in the table, included both face burn and eye injury. In one incident, an employee died after inhaling the hot gases from the electric arc [56].

tric arc poses a substantial risk of nonburn injuries. . . less well known. . . frequently less severe than the potentially threatening burn injuries [55].” Table X provides a summary of the original analysis and an additional nonburn injury analysis of 95 OSHA records released between 2005 and 2008 [56]; 14.7% of the 2005–2008 records reported nonburn injuries. It is likely that many of the OSHA records did not document any or all of the nonthermal burn injuries that occurred. It should be noted that eye injuries and hearing damage can result from serious thermal burns, as well as the respective effects of light and sound. The nonburn injury data in Table X also includes reports of smoke inhalation and asphyxia. Intense arc temperatures can vaporize the electrodes (typically copper or aluminum) and adjacent enclosure walls (typically carbon steel). It has been estimated that vaporized copper has a volume which is 67 000 times larger than its original solid form [57].The workers probably suffered smoke inhalation or were asphyxiated due to the conductor and enclosure metal vaporization or combustion byproducts from the ignition of insulation, paints, and other materials used in the manufacturing of electrical equipment. Exposure to the gases released during an arc event can result in permanent lung damage and the development of lung disease. A study of 1984–2007 OSHA records found that of the 532 records located with keywords “electric arc” and “burn,” 62% occurred on low-voltage systems (LV); of the 329 low-voltage incidents, 66% involved 480 V. However, the percentage of 480-V incidents may have been much higher, since the voltage level was not recorded in 26% of the LV incidents. Table XI briefly summarizes the type of injuries involved based on the system voltage. Some workers were also shocked during the arc incident, particularly on medium- and high-voltage systems (MV/HV). An overwhelming, 86%, of the LV fatalities occurred on three-phase, 480-V systems.

GAMMON et al.: ELECTRICAL SAFETY, HAZARDS, AND THE 2018 NFPA 70E, TIME TO UPDATE ANNEX K?

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Tammy Gammon (S’91–M’99–SM’06) received the B.S., M.S., and Ph.D. degrees from the Georgia Institute of Technology, Atlanta, GA, USA, all in electrical engineering. Since 2003, she has been a Senior Electrical Engineer with John Matthews & Associates, Cookeville, TN, USA. She performs research and analysis in power and power quality issues, in fires of electrical origin, in electrical arc and shock injuries, and in product design and manufacturing. Dr. Gammon is a Licensed Professional Engineer in the State of North Carolina. She served as the Research Manager for the IEEE/NFPA Arc flash Research Project from 2006 until 2014.

Wei-Jen Lee (S’85–M’85–SM’97–F’07) received the B.S. and M.S. degrees from National Taiwan University, Taipei, Taiwan, and the Ph.D. degree from The University of Texas at Arlington (UTA), Arlington, TX, USA, in 1978, 1980, and 1985, respectively, all in electrical engineering. He has been involved in research on arc flash and electrical safety, utility deregulation, renewable energy, smart grid, microgrid, load forecasting, power quality, distribution automation and demand side management, power systems analysis, online realtime equipment diagnostic and prognostic systems, and microcomputer-based instrumentation for power systems monitoring, measurement, control, and protection. Since 2008, he has also served as the Project Manager for the IEEE/NFPA Arc flash Research Project. He is currently a Professor with the Department of Electrical Engineering and the Director of the Energy Systems Research Center at UTA. Prof. Lee is a Registered Professional Engineer in the State of Texas.

Zhenyuan Zhang (S’13) received the B.S. degree from Chang’an University, Xi’an, China, in 2007. He is currently working toward the Ph.D. degree in electrical engineering in the Energy Systems Research Center, Department of Electrical Engineering, The University of Texas at Arlington, Arlington, TX, USA. His focus lies in arc flash research, but he has also been involved in hybrid energy storage, smart grids, renewable energy, electrical safety analysis, and power systems analysis. Mr. Zhang has served as a Project Associate for the IEEE/NFPA Arc Flash Research Project since 2010.

Ben C. Johnson (AM’74–SM’90–F’97–LF’07) is presently Senior Consultant for Thermon Manufacturing Company, San Marcos, TX, USA. His career spans a broad range of industrial experience, including 44 years with Thermon and eight years in the petrochemical industry with Ethyl Corporation and Diamond Shamrock Corporation. He was Thermon’s Vice President of North American Sales for five years and Thermon’s Vice President of Engineering for 12 years, responsible for product application design, field and construction services. He was previously Thermon’s Vice President of Research and Development. He is the holder of eight patents in the field of surface heating and is responsible for numerous new product innovations. He has authored or coauthored 19 papers for various societies. As United States delegate to the International Electrotechnical Commission (IEC), he is the Convener for TC31 Maintenance Team 79-30, Electrical Equipment in Flammable Atmospheres, Electrical Resistance Trace Heating and US Technical Advisor for IEC TC27, Safety in Electroheat Installations. Mr. Johnson is a member of the U.S. Technical Advisory Committee for IEC TC31. He served as Cochair of the IEEE/NFPA Collaboration on Arc Flash Research.