Services Description ARC FLASH STUDY

What is Arc Flash Definition?

Arc flash definition according to NFPA 70E is the sudden release of unexpected heat and light energy produced by electricity passing through the air like a lightning. Arc flash is also a phenomenon that is usually caused by accidental connection between live conductors, or between live conductors and the ground. Temperature at the arc point can reach or even more than 35000 Fahrenheit. It is four times the surface temperature of the sun. The air and gas around the arc rapidly heats up and the conductor becomes steam which causes waves called arc blasts. Arc blast is an advanced phenomenon of arc flash events. This article will discuss what the definition, hazard category and risk level of arc flash and arc blast is according to or based on NFPA 70E .

Determinants of Arc Flash Severity

Several groups and organizations have developed formulas to determine the energy available at various working distances from the arc flash. In all cases, the severity of the arc flash depends on one or more of the following criteria:

  •     Short circuit current
  •     System voltage
  •     Gaps
  •     Distance from bow
  •     Opening time of over-current protective devices (OCPD)

Arc Blast Effect

Definition of arc blast is the aftereffect of arc flash. Arc blast is gas and hot air that can cause an explosion equivalent to TNT due to arc flash. The gases released from the explosion also carry products from the arc including molten metal droplets similar to buckshot. High temperatures will vaporize copper expands at a speed of 67,000 times its mass when changing from solid to vapor. Even large objects such as electric panel doors can be ejected a few feet at very high speeds. In some cases, the bus bar comes out from inside the electrical panel which breaks down the panel wall. Explosion pressure can exceed 2,000 pounds/ft2, dropping workers from stairs or even breaking workers’ lungs. This event happened so fast with speeds exceeding 700 miles/hour that it was not possible for a worker to move away.

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