A simplified method for arc flash assessment in low voltage A.C.

Various software are existing to assess the risk of Arc Flash complying with the model provided by the IEEE1584-2018 guide. The empirical model interpolates intermediate values of average arc current, incident energy, and arc-flash boundary to determine final results, corrected by factors for enclosure size and arc current variation. It becomes relevant to have a physical understanding of the phenomenon, examining singularly the various parameters that effect it, such as the arc-flash in air or in enclosure, electrode gap, the box size. In this way, the paper proposes a simplified method to be able to diagnose the computerized results. At first, it proposes the calculation of arc fault currents in the same way than the short circuit currents, analyzing and highlighting the influence of the fault current power factor. Then, this paper proposes a tentative criterion in low voltage a.c.≤600V. It suggests reference values for the arc current in the maximum power transfer condition and so for the incident energy to adopt in the arc-flash boundary evaluation and in the selection of the adequate PPE. The numerical results on case studies obtained with the proposed model and adequate coefficients, considering the arc gap and the box size, are completely consistent with the results obtained with IEEE1584-2018 guide.