I will start by saying that many times this table is misused. It is shown in the standard as an option for determining appropriate PPE, but the notes
1. 25 kA short circuit current available, 0.03 second (2 cycle) fault clearing time.
2. 65 kA short circuit current available, 0.03 second (2 cycle) fault clearing time.
4. 65 kA short circuit current available, 0.33 second (20 cycle) fault clearing time.
and
5. 65 kA short circuit current available, up to 1.0 second (60 cycle) fault clearing time.
are often ignored and make the table inappropriate for use.
In order to use the table, you must determine that the notes apply for your condition. So you have to calculate the arc flash fault current anyway and plot it on the OCPD characteristic curve to see the clearing time.
I have found many times that the clearing time exceeds the time permitted for OCPD clearing time in the notes.
Have others experienced this too?
