The exact method of calculation is different for AC and DC systems as well, so it is critical to have this information available. How to Calculate the Arc Flash BoundaryĬalculating an arc flash boundary is going to be based on the voltage of the equipment that would cause the arc flash. When they are performing this task, here are the things that they will need to do. Calculating where the boundary will be in any given situation is something that should be done by an electrical engineer. This is the level at which it will cause only second-degree burns rather than third-degree. As with approach boundary formulas, use of the IEEE spreadsheet should be the responsibility of an electrical engineer.An arc flash boundary is the distance from the equipment in question to the point where the energy that would be present in an arc flash is 1.2 cal/cm2. Using the IEEE spreadsheet-based calculator.Human error is a potential factor when using such formulas. Note these formulas are complex, require detailed information, and should only be performed by qualified electrical engineers. Using approach boundary formulas available in IEEE Standard 1584 or NFPA 70e ®.Using software designed to calculate arc flash boundaries and create one-line diagrams and approach boundaries required by NFPA 70e.Several ways to do this exist, including: Additionally, an employee who has received on-the-job training and has the ability to perform such duties safely may work within the limited approach boundary under the direct supervision of qualified personnel.ĭetermining Arc Flash Approach BoundariesĪpproach boundaries must be calculated for equipment representing an arc flash hazard. To be qualified to work within arc flash boundaries an employee must have proper electrical safety training, be able to demonstrate the skills needed for safely operating equipment, and an understanding of the hazards involved. No-one should be within this boundary while equipment is energized. The NFPA 70e ® considers the inner arc flash boundary-the prohibited approach boundary-as the distance from an exposed energized component where the effects of an electric arc would be the same as actually touching the live part. Only qualified individuals with energized electrical work permits can work within the restricted approach boundary. The closer an employee is to exposed electrical components the greater the risk of serious arc flash injuries. An unqualified person wearing appropriate PPE can also enter the boundary, but only if escorted at all times by a qualified individual, and then only if informed of arc flash hazards. Qualified workers wearing appropriate personal protective equipment (PPE) can enter the limited approach boundary. The exact dimensions of the limited approach boundary are determined by the equipment’s incident energy risk assessment. Should an arc flash occur, people in the limited approach boundary would be exposed to curable second degree burns of 1.2 calories/cm2. NFPA 70e ® defines the limited approach boundary (also known as the flash protection boundary) as the farthest point at which a shock hazard exists. The NFPA 703 ® recognizes three arc flash boundary levels: the limited approach boundary, the restricted area, and the prohibited area boundary. To lower the risk of arc flash injuries, the National Fire Protection Association ® developed a set of arc flash boundary limits to guide decisions on both equipment operation and personal protective equipment. The results of an arc flash are explosive and violent, and can leave anyone in its path with serious injuries or death. Arc flash describes a dangerous event which occurs when electric current leaves its intended path and arcs through the air until making contact with another conductor or the ground.
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