What Arc Flash Protection Should I Wear?

What Arc Flash Protection Should I Wear?

Voltage Does Not Determine Hazard Category Levels !

Knowing the voltage is only one piece of determining Arc Flash PPE. The available fault current (amps), the working distance between the worker and the equipment, the clearing time of the circuit protection device, the spacing between conductors or from a conductor to ground, the number of phases, whether the conductors are in an enclosure, and the equipment configuration are also needed to determining the potential Arc Flash exposure level and the required PPE. 

NFPA 70E Table 130.7(C)(9)(a) is organized by system voltage level, but at each voltage or range of voltages, there are several different levels of PPE based on the type of task and the equipment as well as on footnote information for fault current and clearing time. For example, a 600 volts system could have a hazard level ranging from Hazard Risk Category (HRC) 0 (PPE up to 2 cal/cm cm2) to HRC 3 (PPE up to 25 cal/cm2) depending the task, the type of equipment and the footnote information on fault current available and clearing time.

The bottom line is that you cannot rely on voltage alone to figure out what arc flash protection you need. You will need to know all the factors noted above and conduct a hazard analysis to determine the potential arc exposure level. In lieu of a formal hazard analysis, you could use NFPA 70E Table 130.7(C)(9)(a) to determine the hazard risk category and Table 130.7(C)(10) to determine the PPE needed for the task. 

Reference: NFPA 70E Table 130.7(C)(9)(a).

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