Arc Flash 3 Flashcards
What is the fundamental difference between analyses done with NFPA 70E vs IEEE 1584?
NFPA 70E does not have an analysis method. It has tables only. The info in Appendix D is only summary and references to other methods, mainly 1584.
What determines the Limited Approach Boundary?
Nominal voltage
What is the relevance of the NFPA 70E Risk Categories?
None. They’ve been eliminated. PPE categories are now based on incident energy calcs (or the 70E Tables).
When would we use the ETAP Quick Arc Flash Calculator?
When the clearing time is taken from another source (e.g., CAPTOR).
What type of equipment represents the most frequent exposures?
LV MCCs (acc to E-2052)
In the arc-flash context, what is an isolated main protection device?
There are sufficient barriers in place to keep a bus-side fault from becoming a line-side fault.
Electrode type VCB
Vertical bus in enclosure (box)
Electrode type VCBB
Vertical Conductor in a Metal Box Terminating in an Insulating Barrier
Electrode type HCB
Horizontal bus in enclosure (box)
Electrode type VOA
Vertical bus in open air
Electrode type HOA
Horizontal bus in open air (no enclosure)
What types of equipment does ETAP default to as having a non-isolated main protective device?
MCCs, panelboards, and switchboards (for our usual equipment, it’s everything but switchgear)
Is ZSI restraint instantaneous?
No. There needs to be a slight delay (approx 20 msec). It’s usually the ST setting that is enabled.
Why does E-2052 say that for a MV motor feeder fault, the incomer should not be restrained?
I think it’s an awkward way of saying that since the motor contribution is high, the motor relay has to be set to not interpret it as a feeder fault.
If two LV devices on a TCC overlap in the instantaneous region, is this necessarily a miscoordination?
No. If the lower breaker or fuse is current limiting, it may still coordinate on a let-through basis.
