An arc flash is a short circuit in the air. The flash is instant, and almost too fast for the eye to understand, however the final outcome of this incident could worth millions in direct and indirect costs to a company.
The temperature of an arc can reach more than 5000 F because it creates a brilliant flash of light and a loud bang. An enormous amount of concentrated radiant energy explodes outward from the electrical equipment, the spread of hot gas, the fusion of metal, causing death or serious radiation burns, and creating pressure waves that can damage hearing or brain function and a flash that can damage eyesight. The fast-moving pressure wave can also send bulk materials such as pieces of equipment, metal tools, and other objects flying, injuring person standing nearby.
When the insulation or isolation between electrified drivers is breached or can no longer withstand the applied voltage, arc flash occurs. Because employees working on or near energized conductors or circuit, movement or close contact with the material, or equipment failure, it can cause a phase ashore or phases fault.
Insulation failure and accidents caused by the probe touching a test on the wrong surface or slid tool are the most common causes of arcing fault. In other words, arc flash is caused by uncontrolled conduction of electric current in the ground phase, the phase of neutrality, or from one phase to be accompanied by ionization of the air. Due to the expansion of the evaporation of metal driver, a line by line or ground fault line arcing can degenerate into an electrical arc fault phase in less than a 1 / 1000 of a second. The heat and intense light at the point of the arc is called arc flash.
Courts-circuits and arc faults are extremely dangerous and potentially lethal to personnel. The proceeds of arc fault current and voltage concentrated in a single place, results in enormous energy released in many forms. Arc fault generates large quantities of heat, which can seriously burn human skin and clothing set on fire. Temperatures in the arc can reach four times the temperature of the suns surface. The high temperature of the arc vaporizes drivers in an explosive change of solid state to steam.
The main reason to be concerned about arc flash is for the safety of staff.
Clyde Lee Dennis
Original source: http://www.articlesbase.com/science-articles/what-you-need-to-know-about-arc-flash-320805.html
