
How does your arc flash calculator deal with single phase faults? 
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"I'm dealing with a number of single phase transformers and considering the possibility of arcing faults at the secondary terminals. I'm not sure how to handle this."
The Duke Power Heat Flux Calculator is most often cited when single phase arc incident energies are to be determined. The Duke Power Flux Calculator guide also explains how to calculate 3 phase arc using single phase arc data (see page 9). The calculator assumes the arc incident is being sustained by a single phase source. The Guide says To correct for the involvement of all three phases, multiply the incident energy value from the Heat Flux Calculator by a factor of 2.8. We do not know the calculation procedure behind the the Duke program as it does not seem to be ever published. However, if you trust the factor, you can use it to calculate single phase arc using three phase arc data obtained using the IEEE 1584 procedure and dividing the resulting value by 2.8.
We find the IEEE procedure more advanced comparing to the Duke because it calculates arc current based on prospective bolted fault current value, geometry and configuration of the equipment. Unfortunately, the Duke software does not give any guidance on how to calculate single phase arcing current using single phase short circuit current value.
Although IEEE 1584 guide has been developed primary for three phase arc fault analysis, the guide states that "A theoretically derived model, based upon Lee’s paper, is applicable for threephase systems in open air substations, and open air transmission and distribution systems. This model is intended for applications where faults will escalate to threephase faults. Where this is not possible or likely, this model will give a conservative result. Where singlephase systems are encountered, this model will provide conservative results."
