An arc flash is defined as a release of energy that is very rapid and happens between the phase bus bar and a separate bus bar, a neutral, or a ground. In the case of such arc flashes, the air itself acts as a conductor of the electricity. These types of occurrences generally only happen with systems that are powered by 110 volts or more. Systems that are powered less than this typically will not be able to sustain such power to make the arc happen. Arc flashes are almost always fatal when there is a human present, this is why it is so crucial to perform a proper arc flash analysis.
To perform such an analysis, there need to be certain steps taken. Firstly, data needs to be collected concerning the power distribution system of the facility in question. This data will include information collected from nameplate specifications which are located on every device. Information on the lengths and areas of a cross-section of outlying cables should also be collected. The utility company will need to be contacted to verify what minimum and maximum fault current levels should be expected.
Usually what happens after this data is collected is that the determination is made that category 4 PPE will need to be put in place. Unfortunately, this type of placement can be both extremely costly and unwieldy. However, the recommendations need to be done as new regulations concerning the analysis of arc flashes make this a legal requirement.
As you can tell, it is extremely important to have these done but it can also quickly become very complicated. It is best to have this done by a professional certification or inspection company to avoid any unknown or unforeseen complications resulting from the misreading of data.