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3 phase fault
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Author:  cooldesign [ Tue Jun 28, 2011 10:57 am ]
Post subject:  3 phase fault
for arc flash analysis, we calculate arcing current based on 3 phase bolted current. what if i wanna calculate arc boundary or incident energy on one phase equipment? do u have to still use 3 phase fault current?

other question is for arc short circuit current, voltage has to be taken into account. this voltage is line to ground or line to line?

pls let me know, i will be appreciated that

jim
Author:  JBD [ Tue Jun 28, 2011 7:15 pm ]
Post subject: 
cooldesign wrote:
for arc flash analysis, we calculate arcing current based on 3 phase bolted current. what if i wanna calculate arc boundary or incident energy on one phase equipment? do u have to still use 3 phase fault current?

You need to use some other methodology other than simply IEEE1584. There is no single industry accepted method. Your company should evaluate all of the possible options and then adopt one which it is willing to defend before a judge and jury.
Author:  cooldesign [ Wed Jun 29, 2011 7:01 am ]
Post subject: 
what is the other methology? what i am trying to ask you, do we do arc flash for one phase equipment? i calculated all 3 phase faults, but i did not calculate one phase fault for single phase lines. do i have to calculate single phase faults currents for arc flash? because i saw in the IEEE1584 starndart, it says arc flash analysis will be done for 3 phase analysis because it is greater than one phase fault current. what if for one phase equpment?
Author:  wbd [ Wed Jun 29, 2011 9:26 am ]
Post subject: 
The most conservative approach is to use the 3 phase values for the single phase equipment.
Author:  JBD [ Wed Jun 29, 2011 9:34 am ]
Post subject: 
wbd wrote:
The most conservative approach is to use the 3 phase values for the single phase equipment.


To you have a reference for that statement?

Isn't the most conservative approach is to assume no PPE is available, therefore "live" work is prohibited?
Author:  cooldesign [ Wed Jun 29, 2011 9:57 am ]
Post subject: 
so, if it is single phase cable or equipment. we need to cut energy off then work for that equipment?

or even if it is single phase, we can use the 3phase fault current?
Author:  SCGEng1 [ Wed Jun 29, 2011 10:06 am ]
Post subject: 
cooldesign wrote:
for arc flash analysis, we calculate arcing current based on 3 phase bolted current.


What kVA, fault level, and voltage are you talking about here?
Author:  cooldesign [ Wed Jun 29, 2011 10:23 am ]
Post subject: 
i have some 25kva one phase transformers, i am getting 3 phase fault currents around 800 amps, voltage level is 240 volts
Author:  JBD [ Wed Jun 29, 2011 6:12 pm ]
Post subject: 
cooldesign wrote:
i have some 25kva one phase transformers, i am getting 3 phase fault currents around 800 amps, voltage level is 240 volts


I believe the accuracy/reliabilty of IEEE1584 falls off around 750A of arcing fault current.
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