Common Causes of Arc Flash

By: Mike Enright

Occurring 5-10 times per day in the United States and resulting in over 400 fatalities and 30,000 incidents a year, arc flash occurrences are common, dangerous, and often deadly incidents.

Arc flash injuries are different than common electrical shock injuries; while electrical shock injuries occurs when current passes through the body, the risk from an arc flash comes from concentrated energy during an arcing fault. The energy of an arc flash has the power to instantly vaporize metal including copper and steel, exposing a worker to temperatures that can reach or exceed 35,000 °F, blast pressures that could destroy concrete, and shrapnel from an arc blast.

Arc flash incidents can occur in an instant, with a line-to-line or line-to-ground arcing fault can escalate into a three phase arcing fault in less than a 1/1000 of a second. Whether these incidents result in severe burns (the most serious burns are usually the result of clothing ignition), blindness, loss of hearing, or one of the many other injuries that could occur, these injuries are absolutely debilitating, and it’s common that an injured employee never regains past quality of life.

Causes of Arc Flash Hazards

While human error or carelessness of a worker account for the majority of incidents, arc flash can be the result of a wide variety of causes—static electricity, loose connections, or even a rodent in the vicinity that compromises the distance between energized components.

Human Error and Carelessness

No matter how well trained a worker is, accidents happen and are often the result of operator error. Distractions, weariness, pressure to get the job done quickly, or simply overconfidence can cause a worker to move too fast, fail to don personal protective equipment (PPE), or bypass other safety procedures. It’s estimated that two out of every three arc flash incidents occur as a result of human error and carelessness.

Often is the case, a worker will complete the same task many times over the course of a year, a decade, or a career without incident, developing bad habits while trying to save time. It only takes one mistake to cause the electrical current to become uncontrolled, even something as routine as a control panel adjustment could end up with deadly consequences.

Additionally, failure to verify absence of voltage, utilizing incorrect testing equipment (i.e. voltage testers), overconfidence, complacency and poor co-worker communication and lack of lockout/tagout procedures have all been underlying root causes of arc flash incidents

A dropped screw or bolt, a tool slipping when he or she applies torque, or a distraction during a critical moment could result in a mistake that leads to the flash.

Failure to Use an Insulated Tool

While this may fall into the carelessness category, many arc flash explosions occur when an employee uses a non-insulated tool that is not designed for the job. A tool slips or gets dropped and without the proper insulation it immediately becomes a conductor for electricity.

Excessive Dust

The result of negligence over the course of months or years, dust buildup can result in a faulted path in the electrical current. This faulted path causes the current to be drawn to another conductor, creating an environment in which arc flash incidents occur.

Corrosion

All equipment has an expectation for routine ongoing maintenance. However, in cost-cutting circumstances, sometimes maintenance is skipped or done incorrectly, jeopardizing the long-term safety of the system. This failure to maintain leads to corrosion, exposing conductive surfaces creating resistance and heat—two of the primary culprits in arc flash events.

Improperly Maintained or Installed Switches and Circuit Breakers

Sometimes negligence isn’t the culprit—sometimes normal wear and tear could result in environment ripe for an arc flash incident. Other times, proper installation procedures may not have been followed. Both instances create an unsafe environment for workers operating on an energized environment, as improper installation can make it difficult or impossible for electricity to follow the intended path, which can cause an arc flash.

Use of Substandard Parts

One of the most avoidable mistakes that could lead to an arc flash injury is the failure to use parts that are rated for the equipment on which they are being used. Because electrical equipment parts are rated for certain levels of current, using a part that is not appropriately rated for its application can lead to an arc flash situation.

Condensation, Water, or Other Liquid near Electrical Equipment

If condensation or other liquid is near a conductive surface, electricity may escape the wiring through the water, and then the arc flash will occur as the electricity seeks its destination.

Minimizing Risk of Injuries from Arc Flash

There are many ways to minimize arc flash risk when it’s not possible to deenergize the source, and many of them rely on following safety standards set by OSHA, NFPA, and more including basic features like lockout/tagout, approach boundaries, and labeling needed to avoid injury risk in the event of an arc flash.

Knowing this, one of the most important parts of safely working on equipment in which an arc flash may occur is to take necessary steps to protect yourself or your people. Training and retraining employees, deenergizing equipment, and suppling workers with effective and compliant personal protective equipment (PPE) are all necessary parts of an effective risk avoidance strategy as it pertains to arc flash hazards.

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From Carelessness to Culture: Developing an Electrical Safety Culture

As noted above, human error and carelessness are the top reasons accidents occur. Even if you have an electrical safety program in place, once one thing slips, behaviors start to snowball. A shortcut turns into a habit and a habit becomes a behavior until one day employees start to believe that “it’s the way we do things around here.” Too often, things don’t change until a near miss, an inspection, or worse. If you are looking to minimize the likelihood for errors and careless actions, an employee-focused safety culture can help. Developing a Culture of Electrical Safety explores the differences between a compliant program and a true culture of safety while offering tips that can make your people safer. Preview this guide below and download it here.

Related Reading:

10 Common Causes of Arc Flash and Other Electrical Accidents

What is Arc Flash