![]() Take the proper steps to ensure your safety before taking any measurements, especially on energized equipment. Arc fault incidents happen daily in the United States. The boundary was thus eliminated in order to prevent confusion and to make the 70e standard easier to use and understand.ĭespite being eliminated as a health and safety standard, the PAB may still be used within the context of electrical research or for documentary purposes. The arc flash boundary is the minimum safe distance from exposed energized conductors or circuit parts that has the potential for an arc flash. While the limited approach boundary marks the closest point at which an unqualified person can approach exposed energized equipment, and the restricted approach boundary marks the point at which workers must wear shock-protection equipment, the prohibited approach boundary did not mandate any new action be taken by workers. ![]() The PAB was eliminated because it did not trigger a mandatory action by employees. This boundary is calculated based upon specific system information, and can. ![]() It is defined as the distance at which a worker is exposed to 1.2 calories/cm2 of incident energy, which represents the onset of a second degree burn. The limited and restricted approach boundaries, as well as the arc flash boundary, remain in effect. The arc flash boundary is a critical component of electrical safety programs, as it helps to identify potential danger areas and ensure that workers are aware of the hazards. The Arc Flash Boundary deals specifically with arc flash hazards and determines when arc flash PPE shall be required. It was eliminated by the NFPA in the 2015 edition of the 70e standard. The PAB was developed by the National Fire Protection Association (NFPA) as part of its 70e standard governing electrical safety. The two lower-risk approach boundaries are the restricted approach boundary and the limited approach boundary (lowest risk). The arc flash boundary is independent of the shock protection boundaries. We must utilize proper PPE for arc flash protection when inside this boundary. The prohibited approach boundary is the most high-risk of three approach boundaries used to delineate risk-level zones around electrical equipment. This boundary is a distance at which a worker could suffer a 2nd-degree burn in 1 second to exposed bare skin. The flash protection boundary is based on voltage, the available fault current and the time it takes for the upstream protective device to operate and clear the fault. Safeopedia Explains Prohibited Approach Boundary The working distance is the distance from a person’s face and chest to the prospective arc source. The flash hazard analysis should determine the flash protection boundary (FPB) and level of personal protective equipment (PPE) that the worker must wear. The two major arc flash boundaries are: The Limited Approach Boundary: This is the minimum distance from energized equipment where unqualified and unprotected persons may safely stand.
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