This calculation establishes various arc flash boundaries and specifies the Personal Protective Equipment (PPE) required when approaching each boundary. The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extraordinary force.Īn Arc Flash Study or Analysis is a calculation performed by Professional Engineers to determine the incident energy at each location. Arc flash temperatures can reach or exceed 35,000 ☏ (19,400 ☌) at the source of the arc. This video demonstrates the devastating effects of a large arc flash. A large arc flash can easily generate incident energy in the range of 40 cal/cm2 Higher incident energy can cause third-degree (incurable) burns. If unprotected skin is exposed to an incident energy of 1.2 cal/cm2, a second-degree (curable) burn is expected. Incident energy is measured in calories/cm2. This is why its important that protective devices be properly set and coordinated in order to identify the beginnings of an arc and quickly interrupt the fault. If there is enough power available, an arc flash could last an extended period of long time. Also known as the “working distance”, this measurement is estimated to be 18 inches.ĭuration - How long the arc will last. This is calculated using the system voltage and the maximum available fault current.ĭistance - How far away a from the arc worker will be. In most cases, arc flash incident energy depends on three elements: The radiant energy released by an electric arc is capable of permanently injuring or killing a human being at distances of up to ten or even twenty feet. If you sit right next to a campfire, you would receive more radiant (incident) energy than if you sit farther away. Incident energy of an arc flash can be best explained with a simple campfire analogy.

The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extraordinary force. Many of these workplace injuries result from arc flash, a type of electrical explosion that occurs due to a low-impedance connection to ground or another voltage phase in an electrical power system.Īrc flash temperatures can reach or exceed 35,000 ☏ (19,400 ☌) at the source of the arc. Numerous workers are injured or killed each year while working on energized electrical equipment. Arc Flash Hazards: NFPA 70E Working Boundaries Explained 897×550 107 KB

Arc flash boundary poster