Common causes of arc flash incidents

Working around exposed, live parts presents a hazard and, the fact is, accidents do happen. When it comes to accidents around electrical equipment a mere drop of a tool or physical contact with the live part can set off an arc flash and instantly generate an energy explosion releasing temperatures in excess of 35,000˚F.

Adding or removing circuit breakers, contactors or components in energized control circuits or motor control center (MCC) buckets, or installing or removing MCC buckets from a live bus, can incite an arc flash. Routine operation of breakers and disconnect switches, especially racking breakers in or out of both low- and medium-voltage switchgear, all present a risk of arc flash in equipment that has not been properly installed, tested and maintained.

The primary purpose of a circuit protective device is to interrupt current flow after a downstream short circuit or fault is detected. If the protective device has not been properly maintained and it fails to interrupt the fault, the result could be an explosive arc flash resulting in damage to equipment and personnel. Regular testing and preventative maintenance can to help ensure the equipment will operate within manufacturers tolerances. Poor environmental conditions such as moisture or a build-up of conductive dust or contaminants can result in corrosion or compromised insulation systems. Damaged or improperly rated tools and test equipment, including worn insulating material for screwdrivers and wrenches, can lead to accidental arcing from conductors to ground.