ARC FLASH HAZARD ANALYSIS BASICS

To perform an arc flash hazard analysis, you need to start by gathering information on the building’s power distribution system. This data should include the arrangement of components on a one-line drawing with nameplate specifications of every device on the system and the types and sizes of cables.

The local utility company should be contacted so that you can get the minimum and maximum fault currents entering the facility.

Next you will want to perform a short circuit analysis and a coordination study. You will need this information to put into the equations provided in NFPA 70E or the IEEE Standard 1584. These equations will give you the flash protection boundary distances and incident energy potentials you will need to determine your minimum PPE requirements.

In many ways an arc fault analysis is actually a study in risk management. You can be very conservative in your analysis and the results will almost always indicate the need for category 4 PPE.

On the other hand, you can perform the analysis and make adjustments to reduce the arc fault conditions resulting in reduced PPE requirements.

However, use caution when adjusting your calculations. Reducing the bolted fault current can reduce the arc fault current, but it can actually result in a worse situation.

For example, if you reduce the current applied to a motor from 4000 to 1800 A, the arc fault energy is increased from 0.6 to 78.8 cal/cm2. This is the exact opposite outcome that you might expect to achieve before doing the math.

Keep in mind that you are risking OSHA violations and fines if you choose nominal compliance. On the other hand, you can actually be increasing the risk of injury if you force workers to unnecessarily wear cumbersome PPE.

This can also result in little or no high voltage maintenance being performed, which will eventually compromise safety and proper equipment operation. It might prove beneficial to get a registered professional engineering firm to perform arc flash hazard calculations on your behalf and have them recommend appropriate actions and the lowest appropriate category of PPE.