Incident POWER of an Arc Flash Event

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Has anyone else investigated the work done per unit time (POWER) of an arc flash event?

A long term event has a very high incident energy when integrated over time, but escape from harm is possible for low explosiveness (W/in^2) ratings. (Future IEEE 1584 work?)

I've seen 100W/in^2 to 1kW/in^2 resulting in level 5 HRC levels (over 70E allowable).

Any ideas / comments?
 

ron

Senior Member
Re: Incident POWER of an Arc Flash Event

Your findings are not unusual. I can't verify your w/in^2 information, but in many incident energy calculations, values in excess of 40 cal/cm^2 (or >PPE4) is the result.
Very often it is a result of low bolted fault current and the resultant arc flash fault current that gives slow clearing time to the OCPD.
 
Re: Incident POWER of an Arc Flash Event

Thanks for the reply Ron.

What I'm getting at, is a determination of the explosiveness of an event; i.e., at what power density can a level 5 HRC be reduced to workable PPE. Current standards only address incident energy.

I expect IEEE 1584 to address this issue. I am looking for insight . . .
 

jim dungar

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PE (Retired) - Power Systems
Re: Incident POWER of an Arc Flash Event

Right now the standard PPE is for flash protection. There is nothing really offered for blast (shock wave) protection. The blast seems to become more of an issue above HRC4 (40cal/cm2).
 
Re: Incident POWER of an Arc Flash Event

Jim you are correct on the blast, what I'm driving at is "non-explosive" events which have Ei > HRC4.

I am looking for an engineer who has EXPLORED, and has MANAGEMENT ACCEPT, parameters and HRC reduction levels for an escapable "non-explosive" event in which Ei > HRC4.

I'm dreaming if I expect a direct answer, but I thought I'd run it through the forum . . .

We have panelboards with HRC > 4 (supplied by XFM >= 125kVA) but trip times are high (>> 2 seconds). Under current conditions I have to bring the entire system down to replace a breaker. Or use the IEEE 2 second exit time and reduce the HRC . . . Reality check required . . .

Dave
 
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