Lower ka limit for arc flash calculation
Lower ka limit for arc flash calculation
(OP)
I have been reading a number of articles recently dealing with arc flash. In one of the articles I came across a statement advising that below a certain value of fault current (ka) and a certain size of circuit breaker it is not worth conducting an analysis as the category will be zero. I think the values were 25ka and 100 amp, 433v 3 phase. Unfortunately I have not been able to locate this article again. I am interested in confirming these values as I am writing a standard operating procedure (SOP) dealing with arc flash and have made the statement that this analysis is required on all "high fault current circuits". I am therefore looking for a definition (lower cut-off point) for "high fault current".
Thank you for your help.
Thank you for your help.






RE: Lower ka limit for arc flash calculation
RE: Lower ka limit for arc flash calculation
ps; I am in Australia, not the USA
Thanks again.
RE: Lower ka limit for arc flash calculation
This statement refers to the incident energy exposure possible under these conditions as observed during testing. The IEEE statement means that it is not necessary to calculate incident energy on equipment under 240V fed from a transformer less than 125 kVA, because the available fault current is not high enough to sustain an Arc-Flash and release significant energy. It is important to remember that this statement only refers to incident energy calculations, and does not release employers from the responsibility to assess all equipment operating at 50 volts and higher in the workplace for other electrical hazards, such
as shock and overload conditions which may lead to electrocutions, fires, or other hazards.