The Effects of Means of Grounding and Asymmetrical Current on Arc Flash

Industrial power systems bring considerable challenges in terms of safety and reliability. As any other power network these type of systems have some specific risks, specially when it concerns to short circuit faults. These faults create a phenomenon called Arc Flash, which in some cases can be extremely hazardous for the system equipment, and also for the personnel. The IEEE 1584-2018 standard currently presents a methodology in the calculation of Arc Flash where the incident energy level is calculated based on the symmetrical rms bolted fault current value. However, the first cycles of the fault current are not symmetrical values. Therefore, it is necessary to analyze what happens if the incident energy is calculated as stated in the IEEE 1584-2018 standard, but using the rms value of the asymmetrical current. This article takes into account the asymmetrical current into Arc Flash estimations. This current value will affect considerably the level of incident energy during a fault, specially for systems with a high X/R ratio. Additionally, this article will show up an analysis to see what happens with Arc Flash levels in industrial power systems using high resistance grounding, and comparing it with solid grounded systems, one of the most common grounding means in industry. As this study means an improvement on the safeness of electric systems, simulations were carried out using IEEE 242 system in order to support the content of this paper.