Therefore, it's essential to accurately calculate the arc flash boundary for each piece of equipment to ensure that workers are adequately protected.Ĭalculating the arc flash boundary requires an understanding of the electrical system and the potential hazards associated with it. It's important to note that the arc flash boundary distance can vary depending on several factors, including system voltage, available fault current, and protective device settings. However, the NFPA 70E and CSA Z462 standards provide a table that specifies the minimum arc flash boundary for 480V equipment based on the available fault current and the protective device clearing time.įor example, if the available fault current is 10,000A and the protective device clearing time is 0.1 seconds, the minimum arc flash boundary for 480V equipment is 3 feet for a category 1 PPE level. The arc flash boundary for 480V equipment can vary depending on the incident energy level.

The minimum arc flash boundary is the distance from the energized equipment where the incident energy is below 1.2 cal/cm², which is the level of thermal energy that can cause second-degree burns to unprotected skin.

The NFPA 70E and CSA Z462 standards provide tables and formulas to help calculate the incident energy and the minimum arc flash boundary distance. The incident energy level is calculated using complex mathematical formulas that consider the system voltage, available fault current, and the time the protective devices take to clear the fault. The minimum arc flash boundary is determined by the incident energy level that could be released in the event of an arc flash. This boundary is marked with a black boundary line and is used to indicate the most hazardous area. Prohibited Approach Boundary (PAB) - The prohibited approach boundary is the closest distance to the energized equipment considered safe for any person to approach, regardless of PPE.

This boundary is marked with a red boundary line and indicates the point where a worker must begin wearing the appropriate PPE to prevent injury. Restricted Approach Boundary (RAB) - The restricted approach boundary is the minimum distance from the energized equipment a qualified worker can approach without wearing the appropriate PPE. This boundary is generally marked with a yellow boundary line and is intended to keep unqualified personnel from entering the hazard zone. Limited Approach Boundary (LAB) - The limited approach boundary is the minimum distance from the energized equipment that an unqualified person can approach. There are three arc flash boundaries that are defined by the NFPA 70E and CSA Z462 standards: The NFPA 70E and CSA Z462 standards provide guidance on the minimum distances that should be maintained between energized electrical equipment and workers based on the incident energy levels. The arc flash boundary is the minimum safe distance from the energized equipment that an unqualified worker can approach without wearing PPE. The higher the incident energy, the greater the potential for injury and the larger the arc flash boundary. Incident energy is the thermal energy that could be released during an arc flash, measured in calories per square centimetre (cal/cm²). 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.Īrc flash boundaries are established based on the incident energy that could be released during an arc flash. Implementing an effective arc flash safety program that includes accurate arc flash boundary calculations, appropriate PPE, and specialized training for workers is critical to protect workers from the hazards of arc flash incidents.Īn arc flash boundary is a designated area around energized electrical equipment where an arc flash could cause serious injury or death to a worker not wearing the appropriate personal protective equipment (PPE).

Arc flash boundaries