NFPA 70E Standard for electrical safety in the workplace requires facilities to:

• Train employees exposed to potential arc flash hazards

• Provide Personal Protective Equipment necessary to protect the workers from arc flash hazards

• Conduct an Arc Flash Analysis for your site

Additionally, the 2002 NEC added an Equipment Labeling requirement that covers the majority of electrical equipment in most plants.

National Safety Technology understands that these new requirements can be confusing and requires a large amount of your valuable time researching the requirements and dealing with multiple vendors to meet all of these requirements. NST is your simple solution for meeting these requirements.

 

What is ARC FLASH Arc Flash is the result of a rapid release of energy due to an arcing fault between a phase bus bar and another phase bus bar, neutral or a ground. During an arc fault the air is the conductor. Arc faults are generally limited to systems where the bus voltage is in excess of 120 volts. Lower voltage levels normally will not sustain an arc. An arc fault is similar to the arc obtained during electric welding and the fault has to be manually started by something creating the path of conduction or a failure such as a breakdown in insulation. The cause of the short normally burns away during the initial flash and the arc fault is then sustained by the establishment of a highly-conductive plasma. The plasma will conduct as much energy as is available and is only limited by the impedance of the arc. This massive energy discharge burns the bus bars, vaporizing the copper and thus causing an explosive volumetric increase, the arc blast, conservatively estimated, as an expansion of 40,000 to 1. This fiery explosion devastates everything in its path, creating deadly shrapnel as it dissipates. The arc fault current is usually much less than the available bolted fault current and below the rating of circuit breakers. Unless these devices have been selected to handle the arc fault condition, they will not trip and the full force of an arc flash will occur. The electrical equation for energy is volts x current x time. The transition from arc fault to arc flash takes a finite time, increasing in intensity as the pressure wave develops. The challenge is to sense the arc fault current and shut off the voltage in a timely manner before it develops into a serious arc flash condition.

Steps required for a flash hazard analysis To perform an arc flash hazard analysis, data is collected about the facility's power distribution system. The data includes the arrangement of components on a one-line drawing with nameplate specifications of every device. Also required are details of the lengths and cross section area of all cables. The utility should be contacted for information including the minimum and maximum fault currents that can be expected at the entrance to the facility. Once the data has been collected, a short circuit analysis followed by a coordination study should be performed. The resultant data can then be fed into the equations described by either NFPA 70E-2000 or IEEE Standard 1584-2002. These equations will produce the necessary flash protection boundary distances and incident energy to determine the minimum PPE requirement