What Is Arc Flash?

It is estimated that there are ten injuries per day resulting from arc flash incidents.

An arc flash is not just an electrical arc. For example, although the electrical arc shown in this video is a spectacular arc, it is not an arc flash.

An arc flash is a sudden, explosive arc that usually results from a short circuit fault. It produces a high temperature plasma and a blast shock wave. Metal is vaporized by 5,000+ degree temperatures, creating the plasma. Unvaporized metal is carried by the shock wave as shrapnel. An arc flash can occur in as little a 1/1000 of a second. It is unexpected, violent and deadly.

Even when appropriate personal protective equipment (PPE) is worn, an arc flash can cause injury or death. Workers who are near an arc flash can receive injuries that include severe burns, inhalation of vaporized metal, loss of sight, loss of hearing, puncture wounds and death.

What Causes An Arc Flash?

Anything that causes a phase-to-phase, or phase-to-ground short circuit can cause an arc flash. The short circuit might be caused by a dropped tool, by an accumulation of dirt or debris, even by bus bars that have been bent by excessive current. Are high voltage levels required to create an arc flash? No. Most arc flashes happen on 120v to 480 v equipment, and can happen at voltage levels as low as 50 volts. When it comes to arc flash, don't make assumptions.

Don't rely on techniques and devices such as passive ultrasonic analysis, current limiting fuses or infrared scans of our equipment to provide full protection against arc flash. These are excellent tools that can help to prevent arc flash injuries, but you should not bet your health or life that these tools will be 100% effective.

How Are Arc Flash Injuries Prevented?

NFPA 70E specifies steps that should be taken to minimize the potential for an arc flash injury. The most effective step to take is to de-energize equipment before working on the equipment. However, this is not always possible.

Other than de-energizing, there is no one sure-fire way to prevent an arc flash. But, there is a lot you can do to reduce the likelyhood of an arc flash injury.

Many arc flashes occur when a breaker is racked or a panel door opened. Remote racking, and remote door openers/closers have been developed to provide a safe distance between the device and the worker. This keeps workers out of the potential arc flash blast zone. If remote operation is not available, never stand directly in front of a breaker or panel door. The major force of an arc flash blast hits whatever is directly in front of the device. Standing to the side can greatly reduce the severity of any injuries should there be an arc flash.

A key component of any arc flash safety program is proper labeling of arc flash hazards. A recent survey shows that only 14% of equipment installed before 2002 has arc flash labels. Many accidents are caused by people not thinking before they act. Having equipment properly labeled helps prevent this from happening.

Ensuring that workers are wearing the correct PPE is also critical. PPE is the last line of defense that provides protection when all else fails. Never take short-cuts with PPE.

An arc flash can be created by a variety of causes, prevention and protection requires a variety of defenses be used.

This Arc Flash Article by Steve Hudgik