Electrical, High Voltage Arc Flashes: What You Need to Know


Electrical Arc Flash Image

You’ve heard about arc flash, but do you really understand enough to protect your workers?

Arc flash is a topic that is undergoing increased discussion in the workplace safety and health industry. And with good reason, as according to the National Fire Protection Association (NFPA), fatalities due to arc flash occur at a rate of approximately one per day in the USA. And annually, more than two thousand workers are admitted to intensive care burn units because of these catastrophes.

An arc flash represents an extremely dangerous condition in the workplace. If you don’t have an adequate safety program in place, your workers may be exposed to these dangers. Let’s review some of the basics and look at what occurs during an arc flash incident, as well how to prevent hazardous conditions.

What Is an Arc Flash?

An electric arc is a form of electric discharge, which may be defined as a luminous electrical discharge between two electrodes or other points. When controlled, electric arcs have many industrial purposes. Early public lighting widely used the application of electric arcs. And it is the principle that welders and plasma cutters use today.

But when a system failure happens, electric arcs can occur which are unintentional or uncontrolled, such as an arc flash, which passes through the arc gap caused by faults or short circuit conditions.

According to OSHA:

An arc flash is a phenomenon where a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to ground.

Here's how we explain it in our online arc flash training course below, which introduces the concept of arc flash.

Arc Flash Hazards

Arc flashes can be extreme and violent in nature, due to the large amounts of energy that are expelled. As the arc flash ionizes the air, temperatures may reach or exceed 35,000 °F (19,400 °C). That's hotter than the surface of the sun!

If people are in proximity during an arc flash, clothing can ignite, and severe burns can occur due to these intense temperatures. Secondary fires may also occur if combustibles are near the event.

These temperatures can also cause metal parts nearby to liquify and vaporize. As the metal changes from a solid to a gaseous state, the rapid expansion can produce pressure and an explosion or blast. The intense energy pressure (2,000 lbs/sq.ft) radiates outward and can strike workers, like a bomb, knocking them off their feet, or throwing them backward, often causing compression injuries. Blinding light, deafening noise, flying shrapnel, and molten metal can be produced in these arc blast events.

Arc Flash Injuries

Fatalities and serious injuries can occur, given these hazards. Third and second-degree burns over a significant portion of the body, as well as permanent disabilities, such as vision or hearing loss, are not uncommon.

The severity of the arc flash injury depends upon:

  1. How close a person is to the hazard
  2. The temperature the person was exposed to
  3. The time for the circuit to break

What Causes an Arc Flash?

Several factors can lead to arc flash, including:

  • Accumulations of conductive dust
  • Deterioration of equipment
  • Dropped tools
  • Accidental contact with energized parts
  • Condensation on equipment
  • Material failure
  • Corrosion
  • Faulty installation
  • Distracted or untrained workers

One way to think of arc flash causes is to separate them into arc flashes caused by humans and arc flashes not caused by humans.

Here are some ways humans can cause arc flashes:

And here are some ways arc flashes can occur without human causation:

How to Avoid Arc Flash Events

Numerous methods exist to protect workers from the hazards associated with arc flash and electric current. Most arc flash events are preventable. Human error, such as distracted workers or using conductive tools to perform energized work, results in many arc flash events.

With arc flash training, safety procedures, arc flash risk assessments, proper PPE, and appropriate non-conductive tools for energized work, employees can avoid these hazardous conditions. Routine maintenance, which minimizes equipment failures, combustible dust, and corrosion, can also help prevent arc flash.

These are not a haphazard process to avoid arc flash. Instead, there is a system which has been developed by the National Fire Protection Association (NFPA) that is based on the best scientific evidence and allows for maximum protection of workers.

And of course, the safest route is to eliminate the hazard altogether. Is energized work necessary for all tasks your maintenance workers perform? Could lockout/tagout be used instead? Employers should examine the current procedures. It is not uncommon to find that energized work is chosen by workers as a “shortcut” instead of performing lockout/tagout.

Preventive Measures

If energized work must be performed or employees have risk of exposure to live equipment, you will need to get familiar with the appropriate safety standards. NFPA 70E is the national consensus standard for electrical safety in the workplace, and it details the methods employers should take when workers must perform energized work.

Among these steps are determining the appropriate boundaries for electrical workers to observe, as training, PPE and other protections will vary according to the hazards present. Two boundaries specifically pertain to shock or electrocution hazards, while the third is designated toward preventing arc flash events.

The NFPA list the three boundaries as:

  • The restricted approach boundary
  • The limited approach boundary
  • The arc flash boundary

In the first two, voltage levels determine their boundaries. These may be found by referring to the NFPA 70E tables.

However, the arc flash boundary requires a more complex analysis, which determines flash hazards present, and calculates incident energy, from which safe work practices are developed, equipment is appropriately labeled, and corresponding PPE is selected.

In the 2015 NFPA 70E, two methods are listed to determine the necessary PPE for various job tasks. The first, the Flash PPE Category Method uses tables found in the 70E, while the second, the Incident Energy Analysis Method, applies detailed calculations. The NFPA allows either method to be used, but only one may be used per piece of equipment.

If there are any variations or deviations from the NFPA table parameters listed, employers must choose the more intricate, incident energy analysis method.

The sample video below from our online arc flash training course begins to introduce the boundary issues.

But either option allows for the employer to find the appropriate safeguards to protect workers. Choosing correct arc flash PPE, training workers, and following correct safety procedures can prevent arc flash events and ultimately- save lives and reduce risk of injury.

To learn more about these essential protective measures, choose our online Introduction to NFPA 70E training course, which describes the main components of a workplace Electrical Safety Program as well as vital details on safety boundaries. The course also discusses methods to select PPE and requirements for electrical equipment, which are also covered by the NFPA 70E.

Here's a sample of that Introduction to 70E course:

And for all workers with exposure to arc flash hazards, choose our online Arc Flash Safety training course, which introduces the explains the hazards of arc flash and presents various methods to prevent and protect against those dangers.

Conclusion: Arc Flash Is a Serious, Potentially Fatal Workplace Hazard

As you've seen, arc flash is an extremely hazardous occurrence, but there's a lot you can do to reduce the risks at your workplace. As always, safety efforts should begin with a robust safety and health management system at work and should include proper safety training, procedures, and PPE.

And don't forget to consider our online arc flash training course and our online NFPA 70E training course.

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