#Arc flash boundary skin
If unprotected skin is exposed to an incident energy of 1.2 cal/cm 2, a second-degree (curable) burn is expected. Incident energy is measured in calories/cm 2. 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. Duration - How long the arc will last.Also known as the "working distance", this measurement is estimated to be 18 inches. Distance - How far away a from the arc worker will be.This is calculated using the system voltage and the maximum available fault current. Intensity - How much power the arc has.In most cases, arc flash incident energy depends on three elements: The radiant energy released by an electric arc is capable of permanently inuring 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 best be 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 are a result of arc flash, a type of electrical explosion that results from 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 and/or killed each year while working on energized electrical equipment.
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