About Arc Flashes

Understanding Arcs

An electric arc is a complex phenomenon that is just being better understood in the electrical world. Arcs are basically ionized gases cause when electricity travels through air. Arc flashes, arc blasts, electric arc are really all different names for the same basic phenomenon. There are three primary issues in arcs from an electrician's point of view:

Thermal

Pressure Wave

Current Flow

Electricity begins to travel through air because of a breakdown of insulation from air or another insulator causing air to ionize spinning off the outer shell electrons from air. This ionization has two effects: blast and radiation release. The blast is a function of fault current, container size and a few other parameters including magnetic forces. The pressure wave is not as well documented as the thermal effects but it is real. Standards do not tell us what the cutoff is for arc blast but good understanding key. If you have greater than a 40 cal/cm² exposure you should seek engineering guidance to see if it is safe to de-energize or work live. Remember de-energizing can cause an arc if equipment fails or is not designed to be safely de-energized in the manner you are using. The thermal portion of the arc is very well understood and standards like NFPA 70E, NESC, and CAN/UL S801 have reasonable guidelines for determining arc flash energies and some guidelines on clothing worn.

The effect on clothing is interesting, and the field of research is growing in many ways that are not getting much publicity but that can affect the effectiveness of your arc flash program. Usually in the popular literature you will hear of two types of arcs, but there are actually four types of arcs and the last two are rarely considered in arc hazard assessments and only cursorily addressed in the arc flash calculations.

The four types of electric arcs are:

Open air arc (this is the primary arc used in arc testing)

Arc-in-a-box (this is used in one form for arc testing in the EU)

Ejected Arc (when arc plasma hits the worker)

A tracking arc (most common at higher voltages, arc plasma conducts on skin or through clothing)

Only the first two are considered in the calculations and standards. The open air arc is well understood. In lab testing, we control movement of the arc for the sake of repeatability, but in real life from 480V higher the open air arc can quickly turn into an ejected arc or a tracking arc. The tracking arc is most common at very high voltages or during an electrical contact.

Arc flashes are not the biggest killer of electrical workers. Training must include full electrical safety principles and solid risk analysis. Our founders were some of the first researchers in arc flash. We didn't just jump on the arc flash bandwagon. Our training encompasses full understanding of arc flash, arc blast, shock and other hazards of electricity. Companies who have used our services are listed in our clients pages. We have trained more than almost all our competitors combined and are the only company offering our materials through a train the trainer developed by an adult education specialist. Try the e-Hazard difference. No clothing hype, no equipment sales, no pushy sales engineers, just solid NFPA 70E trainers who care about companies and workers alike.

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