How does an arc flash occur?

How does an arc flash occur?

An arc flash will occur when there is a path of lower resistance exists between the electrical system and some other point than exists within the electrical system. Normally, electrical systems, and especially electrical wires, are well-insulated to make it very difficult for the electricity to pass outside of the system. If the insulation is damaged or improperly installed, however, the electricity can most easily escape, resulting in the arc flash.

Even with exposed wires, an arc flash won’t necessarily happen right away. If the electricity can flow through the wires with little resistance, it will not ‘jump’ outside the wiring to another point. If the level of electricity rises, or the resistance outside the wiring lowers, an arc flash will likely occur. This is one of the things that makes arc flashes so difficult to predict. While knowing exactly when an arc flash will occur in a system is difficult, it isn’t difficult to spot potential areas where the conditions that make an arc flash possible are present.

Causes of Arc Flashes

Knowing that an arc flash will occur when there is a path outside of the electrical system that the current can easily flow is important. Understanding some of the most common specific causes of these arc flashes will make it much easier to spot them in the workplace so that they can be repaired before the arc flash ever occurs. Some common situations that will result in an arc flash are as follows:

  • Dusty Work Environment – Dust is a good conductor of electricity, so if there is a buildup of dust in the area around an electrical system, the risk of an arc flash will rise significantly.
  • Uninsulated Tools – When someone is using an uninsulated tool to work on an electrical system, it can easily create a low-resistance path for electricity to travel. This is especially dangerous because the electricity can move into the tool, and then into the person holding the tool, in an instant.
  • Carelessness – When an employee is careless or over confident, they can make mistakes that results in an arc flash. This could be insulating a system incorrectly, placing conductors to close to each other, or any number of other things.
  • Corrosion – Over time, wires and other electrical systems can corrode, which can expose the electricity to the open air where it is at a much higher risk of creating an arc flash.
  • Water or Other Liquids – Water can conduct electricity better than air, and can quickly create a path for the current to travel. This doesn’t have to be standing water. High humidity, splashes, or other similar issues can trigger this type of event.
 

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Additional Resources

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Arc Flash Labeling Guide
 
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