An arc flash occurs when a conducting object approaches an exposed, high-amp electrical source. Most incidents occur on 120 to 240V equipment, and can occur at voltages as low as 50V. Whenever energized equipment is being worked on, there is a danger of an arc flash. Dropped tools or other sources of sparks near energized equipment, gaps in insulating materials which expose conducting surfaces, corroded or improperly installed or maintained equipment can make an arc flash more likely. An arc flash can also occur when removing panels and opening electrical equipment doors, racking breakers, opening and closing breakers, or taking voltage measurements.
The air in the vicinity of an arc flash is heated to between 5,000 and 35,000 degrees in as little as 1/1000 of a second; becoming electrically-conductive plasma that can be unexpected, violent, and deadly. An arc flash is a sudden, explosive electrical energy that usually results from a short circuit fault. The sudden heating can cause a shock wave blast equivalent to several sticks of dynamite and will likely be carrying vaporized metal and shrapnel.
In the United States, between 5 and 10 arc flash incidents occur every day often causing severe injury and sometimes death. Although arc flash incidents are less common than electrical shocks, more than 50% of burn center admittances for electrical injuries are from an arc flash. The temperatures associated with an arc flash can exceed the surface temperature of the sun.
Whenever work must be done on energized equipment, a comprehensive safety program should be in place. Labeling arc flash hazards is an important part of an electrical safety program. In addition to arc flash labels, companies should perform an arc flash analysis, maintain a detailed safety plan, provide adequate personal protection equipment (PPE) for workers, and ensure that workers are properly trained in the procedures necessary to avoid arc flash injuries.
Past posts about Arc Flash:
130 Page Arc Flash Solutions Handbook
