Calculating the Arc Flash Incident Energy in Singlephase Systems using a Three-Phase Model

IEEE 1584 equations do not cover single-phase faults based on the assumption that most of them escalate to a three-phase fault for which this standard applies. If IEEE 1584 equations were used for a single-phase fault, the results would be conservative based on the standard. Most of the short circuit, and fault calculation reference material cover three phase systems. Nonetheless, there are many commercial, and industrial systems, which are single phase. That is, they either feed from a single-phase source, or branch off a 3-phase system. These systems can, too, experience faults, and arc flash, where there aren't good references to cover them. Fault current calculations in single phase systems can be more challenging than a three-phase system due to lack of existing work. In this paper, we present an approach to simulate faults in single-phase systems through a three-phase model. The method is useful since once the equivalent 3-phase model is created both fault, and arc flash calculations can be performed like any other three-phase system. That is, the device curve and the calculated current can be used to obtain the incident energy. The scope, limitations, and details of the method will be presented with some examples.