NFPA 70E Standard defines two main protection boundaries for personnel to observe , including:
– The arc flash protection boundaries
– The shock protection boundaries identified as limited approach boundary and restricted approach boundary.
♦ Limited approach boundary
The limited approach boundary is defined as the distance from an exposed energized electrical conductor or circuit part at which an electric shock hazard exists.
♦ Restricted approach boundary
The restricted approach boundary is distance from an exposed energized electrical conductor or circuit part at which an increased likelihood of an electric shock injury exists.
♦ Arc flash boundary
The arc flash boundary is defined as the distance from the source of an arc at which the incident energy is equal to 1.2 calories per centimeter (Cal/cm2).
♦ Notes:
The shock protection boundaries is not related to arc flash or incident energy. The arc flash boundary may be greater than, less than, or equal to the limited approach boundary and restricted approach boundary.