Arc flash boundary calculator3/24/2024 The results of these equations might not represent the worst case in all situations. The following equations can be used to predict the incident energy produced by a three-phase arc on systems rated 600 V and below. D.3.1 Calculation of Incident Energy Exposure. 793 F V t E = D E = incident energy, cal/cm F = bolted fault short-circuit current, ka V = system phase-to-phase voltage, kv t A = arc duration, sec D = distance from the arc source, in. (4) Rated phase-to-phase voltage of the system. Sound engineering judgment must be used in applying the -second maximum clearing time, since there could be circumstances where an employee s egress is inhibited. Provided by : crawled into equipment will need more time to move away. Single-Line Diagram of a Typical Petrochemical Complex. A person in a bucket truck or a person who has E ELECTRICAL SAFETY IN THE WORKPLACE 015 Editionģ q 30kV/13.8kV q 30kV/13.8kV Public utility 9000MVA fault available 13.8kV Bus 1A 13.8kV Bus 1B 13.8kV Bus 1A/1 600A 13.8kV Bus 1B/1 600A 5MVA 5MVA Bus A 1TI Bus B 4.16kV.5MVA.5MVA 1.5MVA 1MVA 5.57% Bus 3A Bus 3B.5MVA.5MVA Bus 5A Bus 5B.5MVA.5MVA Bus 6A Bus 6B.5MVA Bus 7A 10MVA Bus 4A.5MVA Bus 7B 4.16kV 10MVA Bus 4B Bus 10B Bus 11B Figure D. It is likely that a person exposed to an arc flash will move away quickly if it is physically possible, and seconds is a reasonable maximum time for calculations. If the total protective device clearing time is longer than seconds, consider how long a person is likely to remain in the location of the arc flash. () The total protective device clearing time (upstream of the prospective arc location) at the maximum shortcircuit current. (1) The maximum bolted fault, three-phase short-circuit current available at the equipment. The parameters required to make the calculations follow. The equation that follows can be used to predict the incident energy produced by a three-phase arc in open air on systems rated above 600 V. ft D.4 Calculation of Incident Energy Exposure Greater Than 600 V for an Arc Flash Hazard Analysis. ft Or, using Equation D.1(e), calculate the second degree burn distance using an alternative method: D c = 78. The short-circuit symmetrical ampacity, I sc, from a bolted three-phase fault at the transformer terminals is calculated with the following formula: D c =, = 69. D.1 Basic Equations for Calculating Arc Flash Boundary Distances. The limitations of methods summarized in Informative Annex D are described in Table D.1. It is important to investigate the limitations of any methods to be used. Informative Annex D summarizes calculation methods available for calculating arc flash boundary and incident energy. 1 Informative Annex D Incident Energy and Arc-Flash Boundary Calculation Methods This informative annex is not a part of the requirements of this NFPA document but is included for informational purposes only.
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