Common sources of arc flash hazard in industrial power systems

Electrical design of industrial facilities addresses basic design considerations such as reliability, flexibility, cost and safety. In Europe, arc flash hazards are not always dealt with in great detail beyond reliance on intrinsic equipment safety. Reality is, however, that even with the best equipment design, arc flash accidents still occur, often as a result of human error during work activities. IEEE Standard 1584 has been published as a result of many years of research and empirical testing of the arc flash phenomenon. The standard provides guidance in calculating the arc flash incident energy, taking into account multiple design factors. Incident energy calculations require relatively accurate assessment of the short circuit levels and the characteristics of the protective devices. Such input is conveniently provided by conventional short-circuit and protective device coordination studies. The combination of factors influences incident energy levels rendering some common estimation techniques useless, perhaps even dangerous. For example, a lower short-circuit current can lead to higher incident energy levels because some types of protective devices take longer time to trip for lower current. This paper presents some typical scenarios in industrial facilities that are prone to yield high incident energy levels. The information presented is based on authors' practical experience with arc flash hazard assessments.