Another arc flash question 1

[stevenal]

So with Arcpro in hand, I'm working my way through the system. I'm intentionally looking for long clearing times to find some of the worse case scenarios. What could be worse than a bus fault immediately downstream of a remote substation DY transformer protected by high side fuses? A single line to ground fault here sees lots of impedance and the single phase fault causes the resulting high side current to be shared by two fuses. This particular situation resulted in high incident energy because of a fuse clearing time that exceeded 9s. Even if the exposed worker happened to be injured and could only crawl away, he could still manage to significantly increase his distance from the arc in 9s. Of course the assumption of Arcpro is that he remains in place like a test dummy while he cooks. Does anyone use a smaller maximum clearing time for these situations to take real people into account?

 

[dpc]

IEEE-1584 Annex discusses use of 2 seconds. That what we typically set as a maximum, at least for low voltage. Some people use 2 seconds for low voltage and 5 seconds for higher voltages.

 

[stevenal]

DPC,
That's what I was looking for, missed it before. Thanks.