The term “arc flash” is used to describe low impedance connections in an electrical system, which allows movement of unwanted electric discharge through the air from one voltage phase to another, or to ground. This leads to a rapid rise in temperature and pressure in the air between electrical conductors, causing an explosion known as an arc blast.

Arc blasts and the resulting heat can lead to fires, pressure waves and flying shrapnel that result in serious damage to life and property. These explosions typically occur without any warning, destroy electrical equipment completely and lead to severe injury or death of personnel present within the boundary of the arc flash.

What Are the Main Causes of Arc Flash?

Arc flash occurs when several electrical conductors are placed close to each other, with significant fault currents flowing through them. In this situation, ionization of the air can take place as a result of various factors – such as differences in potential – which leads to a low resistance path and allows current to flow through the air gap between conductors.

Many people assume that low voltage equipment is safe from arc flash, but arc flash hazard levels may be higher at low voltages, due to the high fault currents. Most incidents that occur in low voltage systems are caused by human error, e.g. a tool slipping while a technician works on electrical equipment.

Arc flash can also be caused due to: