Arc Flash

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electro7

Senior Member
Location
Northern CA, US
Occupation
Electrician, Solar and Electrical Contractor
Does anyone know how to do these calculations (see screenshot attached)? Do I need utility transformer information?

It's for a solar PV job and shows on the plans as a required placard.
89d4cace29c67cfba15ef02489afc4ad.jpg


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You can use this calculator if you don't have access to IEEE 1584-2018, but do your research and fully understand what each value means. As a starting point you will need available fault current at the location, which means yes you do need utility transformer information. In lieu of that, you would need to make conservative assumptions of the transformer impedance such that the resulting arc fault current is on the low end to evaluate whether your OCPD trips in the instantaneous range.
 
EC Dan said:
You can use this calculator if you don't have access to IEEE 1584-2018, but do your research and fully understand what each value means. As a starting point you will need available fault current at the location, which means yes you do need utility transformer information. In lieu of that, you would need to make conservative assumptions of the transformer impedance such that the resulting arc fault current is on the low end to evaluate whether your OCPD trips in the instantaneous range.
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I disagree, sometimes you will find that a lower level fault takes longer to trip a breaker which drives up the arc flash hazard. Arc flash is a measurement of total energy released with a magnitude and a duration. More often than not the highest arc flash hazards are due to long duration (depending on type of system of course). I know SKM defaults to 2 second arch duration maximum; i believe that is from 1584 with the thought that a person can get away from an arc in 2 seconds.

If I was the engineer there would be a spec requiring you to perform the calculations. These calcs are very specific to installed conditions so typically they cannot be performed accurately before the specific equipment is selected and even sometimes installed. If there is no spec, ask the engineer for the values to put on the labels. If he wants you to do it, he needs to define the requirements of the calculation. If that isn't in the contract documents, he needs to do it or pay you to have it done by an engineer.
 
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