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Date PostedSeptember 22, 2013

Electrical Arc Flashes and their risks

A hazard that workers on construction sites should become familiar with are Arc Flashes. An arc flash is something that occurs as a result of an electrical fault generating an arc that ionizes the air, leading to combustion.

Surprisingly arc flash is the most common electrical event in the workplace today and yet it often goes unattended. Also the resulting explosion generates the following hazards which can cause severe injuries and even fatalities on site:

  • High temperature
  • Pressure waves
  • Electric shock
  • Sound waves
  • Shrapnel

The amount of energy released during an arc flash event has an impact on the severity of the repercussions and is dependent upon 3 main factors,

  1. Arcing Time – the duration of the arcing fault
  2. Arcing Fault Current Magnitude – the quantity of fault current available in a system
  3. Distance to the Arcing Fault – the distance an individual is from an arc

Managing this risk is important to avoid serious injuries and fatalities. Here are a few tips that can help:

  1. Ensure that engineers who are familiar with the power distribution and the control equipment of the area conduct an electrical system analysis to determine the degree of arc flash hazard.
  2. When working with electrical components and electricity be sure to turn off all electrical power. Lock and tag the circuit out so that no power can flow into the area where the person will be working until all of those involved have used their keys to unlock a padlock.
  3. Ensure that the correct tools are used for electrical work. These tools should include insulated voltage rated hand tools and insulated voltage sensing devices properly rated for the voltage application of the equipment being tested.
  4. Ensure that all electrical distribution system components containing active components such as circuit breakers are properly maintained. The proper maintenance of electrical distribution system components will help prevent an arc flash.
  5. It is useful to apply warning labels to all electrical equipment to foster a culture of awareness to the possibility of an arc flash in worker’s minds.

Knowing the Causes of Arc Flashes can help to overcome this hazard

Poor Maintenance is a common cause of arc flashes so ensure that equipment is properly stored and maintained to prevent this from occurring.  If an energized piece of equipment fails and still has power running into it, the chance of an arc flash occurring is increased. Loose connections can also cause an arc flash by creating space between conductors within the machinery that lead to internal arc flashes. Poor insulation is another cause of arc flashes as it can lead to electrical current escaping from the circuits and entering other parts of the equipment.

Overloading can also lead to arc flashes. This is because when there is too much electricity in the circuit the overload of power will attempt to escape elsewhere, causing an arc flash.

Accidental contact is another cause of an arc flash. For example if 2 pieces of energized equipment that are far enough apart that an arc flash won’t occur touch a piece of equipment with a conductive, metal tool. That additional contact may prove to be the necessary spark that sets off an arc flash.




Peter Cutforth is a Director at Urban E-Learning, a global elearning and web strategy firm based in George St Brisbane. Peter's interests extend to training, safety and compliance, online marketing, and Mobile Apps.

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