can some one shed some light on this item. I am using SKM software to calculate arc flash and I have the option to use a 125 kVa exception that lowers the catagory ratings of my panels fed by transformers below 125 kva. The only thing I can find is "The 125 kVA exception
Often referred to as the “125 kVA Exception,” the 2002 edition of IEEE 1584 contains language that permits a study to exclude calculations on circuits with voltages less than 240V and fed by transformers 125 kilovolt-amperes (kVA) and smaller. This exception was based on a few tests that indicated, that if an arc flash occurs at lower voltages and also with a lower magnitude of short-circuit current, it would be difficult to sustain the arc. Therefore, it would result in a lower level of incident energy.
Since 2002, significant testing has indicated, under certain conditions, it is possible to sustain an arc flash at much lower levels of short-circuit current. Although this exception is still under evaluation and review, it is likely that the cutoff will be greatly reduced from the existing 125 kVA transformer size. "
Is it safe to use this concept???
Often referred to as the “125 kVA Exception,” the 2002 edition of IEEE 1584 contains language that permits a study to exclude calculations on circuits with voltages less than 240V and fed by transformers 125 kilovolt-amperes (kVA) and smaller. This exception was based on a few tests that indicated, that if an arc flash occurs at lower voltages and also with a lower magnitude of short-circuit current, it would be difficult to sustain the arc. Therefore, it would result in a lower level of incident energy.
Since 2002, significant testing has indicated, under certain conditions, it is possible to sustain an arc flash at much lower levels of short-circuit current. Although this exception is still under evaluation and review, it is likely that the cutoff will be greatly reduced from the existing 125 kVA transformer size. "
Is it safe to use this concept???