What is an Arc Flash?
This is the first post in a six-part “Fundamentals of Arc Flash” series. Check back regularly to read new posts offering valuable information on topics such as arc flash causes and characteristics, ratings, and analysis.
Anyone working on or near energized electrical equipment needs to be very aware of the risks associated with an arc flash—and to take the necessary precautions to protect themselves. Failure to do so can result in severe injury or death.
An arc flash is a sudden release of energy that results when a fault or short circuit condition creates a low impedance connection between two electrodes. The resultant flow of energy generates enormous light and heat that radiates outwards at supersonic speeds.
Arc flashes can occur in both high and low voltage environments. Don’t make the mistake of assuming lower voltages mean less risk; 480V arcs are among the most common. An arc flash can generate temperatures of up to 35,000 degrees Fahrenheit (oF) at the arc terminals. By comparison, the temperature on the surface of the sun is estimated to be approximately 10,000oF.
How does an arc flash occur?
An arc flash occurs when electrical energy “jumps” from one terminal to another, to another object, or to ground through a medium that is underrated for the available short circuit current. This can include dropped or carelessly placed tools, accidental touching by a worker, dust, condensation, or corrosion. Because electrical arcs experience negative incremental resistance, the electrical resistance decreases as the arc temperature increases. So, as the arc develops and gets hotter the resistance drops, drawing more and more current until some part of the system melts, trips, evaporates, or provides enough distance to break the circuit and extinguish the arc.
What are the dangers associated with an arc flash?
The enormous heat generated by an arc flash presents the greatest risk to workers nearby. The heat can quickly ignite non-protective clothing, leading to severe or fatal burns. The risk is amplified in the case of clothing made with synthetic fibers that melt and adhere to the skin of the wearer, resulting in even greater injury.
How do you protect against the dangers of an arc flash?
First and foremost, proper safety protocols and procedures should always be followed, beginning with deenergizing whenever possible. When energized work is justified, workers must be in the appropriate arc rated clothing and other required PPE. In addition, regular maintenance schedules must be adhered to in any environment where electricity is present. Human error, corrosion, missing insulation, and even faulty installation are all common causes of arc flash incidents.
No matter how many engineering and behavioral precautions are taken, you should always be wearing arc rated flame resistant (FR) clothing as a last line of defense. Arc rated clothing will not support combustion, and will insulate the wearer from the intense heat of an arc flash up to the arc rating (the amount of energy the fabric can block before the wearer receives a 2nd degree burn). You must ensure you’re wearing clothing that has an arc rating equal to or higher than the possible incident energy.
Want to learn more? Browse our blog posts for more helpful information about protecting workers with FRC and the answers to other frequently-asked questions. Plus, find out about FRC product options and how our managed program can help you maximize compliance and protection while enhancing service and satisfaction.
Have additional questions? Schedule a complimentary 15-minute technical session with Scott Margolin, Tyndale’s Vice President of Technical. Simply complete the form below and Scott will contact you at a mutually agreeable time to speak one-on-one:
