An Arc Flash is an electrical explosion due to a fault condition or short circuit when either a phase to ground or phase to phase conductor is connected and current flows through the air. Arc flashes cause electrical equipment to explode, resulting in an arc-plasma fireball. Temperatures may exceed 35,000° F (the surface of the sun is 9000° F). These high temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. The arc flash / blast will likely vaporize all solid copper conductors which will expand up to 40,000 times its original volume when it is vaporized. The arc flash / blast produces fire, intense light, pressure waves and produces flying shrapnel. When an arc flash happens, it does so without warning and is lightning quick. The result of this violent event is usually destruction of the equipment involved, fire, and severe injury or death to any nearby people. Proper safety and protection measures must be taken to limit the damage from an arc flash which include conducting an arc flash study, short circuit study, and NFPA 70E electrical safety training.
There are a variety of reasons why an Arc Flash can occur, but most of them are human error and preventable. Many arc flashes occur when maintenance workers are manipulating live equipment for testing or repair and accidentally cause a fault or short circuit. Improper tools, improper electrical equipment, corrosion of equipment, improper work techniques and lack of electrical safety training are just some of the events that can lead to a devastating arc flash or arc blast.
An Arc Flash Study/Analysis is a calculation performed by Professional Engineer to determine the incident energy found at each location which determines the various arc flash boundaries and what personal protective equipment (PPE) must be used in approaching each boundary. As part of the study, the engineer should also provide recommendations to reduce the incident engery / arc flash hazard category. An Arc Flash Study / Analysis should only be performed by experienced and qualified electrical engineers familiar with power quality, short circuit studies, NFPA 70E and IEEE 1584.
The following Tentative Interim Amendment (TIA) has been proposed to NFPA. It is being published for public review and comment. The proposed TIA has also been forwarded to the responsible technical committee for processing. The technical committee will consider public comments received by the date indicated below before vote is taken on the...