The important point to note here is that threshold incident energy level for a second degree burn or onset to second degree burn energy on a bare skin is considered constant value equal to 1.2 cal/cm^2 (5.0 J/cm^2) in IEEE P1584 Standard.įlash Fire Burn Experimentations and Observations However IEEE P1584 equations (5.8) and (5.9) for determining the arc flash boundary can also be solved with other incident energy levels as well such as the rating of proposed personal protective equipment (PPE). Quote: " if a butane lighter is held 1 cm away from a person's finger for one second and the finger is in the blue flame, a square centimeter area of the finger will be exposed to about 5.0 J/cm^2 or 1.2 cal/cm^2". To better understand these units, IEEE P1584 refers to an example of a butane lighter. The IEEE 1584 Guide states that " the incident energy that will cause a just curable burn or a second degree burn is 1.2 cal/cm^2 (5.0 J/cm^2 )". Also, NFPA 70E states that " a second degree burn is possible by an exposure of unprotected skin to an electric arc flash above the incident energy level of 1.2 cal/cm^2 ( 5.0 J/cm^2 )" and assumes 1.2 cal/cm^2 as a threshold incident energy level for a second degree burn for systems 50 Volts and greater. The incident energy of 1.2 cal/cm^2 ( 5.0 J/cm^2 ) for bare skin was selected in solving the equation for the arc flash boundary in IEEE P1584. The incident energy to which the worker's face and chest could be exposed at working distance during an electrical arc event was selected as a measure for determining hazard risk category and calculating the arc flash boundary. The IEEE P1584 Standard was developed by having incident energy testing performed based on methodology described in the ASTM F1959-99 standard. Use of Incident Energy as a Measure of Burn Severity in Arc Flash Boundary Calculations The formulas are based on incident energy testing performed and calculations conducted for selected range of prospective fault currents, system voltages, physical configurations etc. Among others, the IEEE Standard P1584 Guide for Performing Arc-Flash Hazard Calculations and formulas provided in Annex D of NFPA 70E and CSA Z462 Workplace Electrical Safety Standard are the most often utilized in the industry to perform arc flash hazard analysis. ![]() During the last two decades different formulas have been proposed to calculate incident energy at an assumed working distance, and the arc flash boundary in order to determine arc rated personal protective equipment for Qualified Electrical Workers. Our interest in determining accurate onset to second degree burn energy and its significance in computing the arc flash boundary is focused on the prevention of injury to the skin of a human who might be exposed to an arc-flash. 1967Įvaluation of onset to second degree burn energy in arc flash hazard analysis ![]() " A.Stoll, Heat Transfer in Biotechnology, Advances in Heat Transfer, v.4. Conversely, measurements of doses which produce the same damage over even a narrow range of intensities of radiation show that the "law of reciprocity" fails, for the doses are not equal. On the contrary, a very large amount of energy delivered over a greatly extended time produces no injury at all while the same "dose" delivered instantaneously may totally destroy the skin. Implicit in this treatment is the assumption that thermal injury is a function of dosage as in ionizing radiation, so that the process obeys the "law of reciprocity," i.e., that equal injury is produced by equal doses. Mathematically it is the product of the flux and exposure time for a shaped pulse. This quantity is defined as the total energy delivered in any given exposure required to produce some given endpoint such as a blister. A glaring example of this process is the "critical thermal load". "Serious misconceptions have crept into this field of research through adoption of rule-of-thumb terminology which has lost its identity as such and become accepted as fact.
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