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Causes of an Arc Flash

An arc flash is when an electrical current "flashes," or flows momentarily through empty air from one conductor to another. These events can be small pops of electrical discharge, or they can be massive outputs of energy on par with huge fireballs and small strikes of lightning that can kill workers and destroy equipment caught in the flash. Knowing what causes these arc flashes and avoiding those situations is one of the keys to staying safe and preventing them from happening.

  1. Overload

    • One of the things that can cause an arc flash is an overload of current. If there's too much electricity in a given circuit, then the overload of power will attempt to escape somewhere. One of the available paths that the spare current can jump to is through the air to another conductor. Normally electricity won't flow through air, but if there is a build up of additional charge in the circuit and there is a nearby conductor (say for example a copper tube or pipe), then the electricity will jump through the air in an arc and establish a connection with that other conductor.

    Poor Maintenance

    • Most equipment, if it's properly maintained, is safe from an arc flash occurring. If an energized piece of equipment breaks down and still has power running into it, then chances are better that an arc flash will occur. Other contributing factors are loose connections within the machinery and poor insulation. The loose connection may create space between conductors within the equipment that will lead to internal arc flashes. In addition poor insulation may lead to electrical current escaping from the circuits and wires and arcing to other parts of the equipment, or from the piece of equipment to another conductor.

    Accidental Contact

    • A third factor that can cause an arc flash is accidental contact. Let's say that you have two pieces of energized equipment that are far enough apart that an arc flash won't occur. Now touch one piece of equipment with a conductive, metal tool. That additional contact may prove to be the necessary spark that sets off an arc flash. For this reason it's important to be careful around energized equipment and to avoid touching it at all. If maintenance needs to be done on pieces of energized equipment, then the power should be shut off and the remaining current properly grounded.

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