DC Arc Flash: Testing and Modeling Incidents in a 125-V Substation Battery Backup System

Station batteries used as a backup source to supply station direct-current (dc) power to relays, etc., present a source of personnel exposure to dc arc flash. However, dc arc flash is less understood compared with the arc-flash phenomena that occur in alternating-current (ac) systems. Some models exist to quantify the potential hazards posed by dc electrical systems; however, there is little empirical data available. Additionally, the lower voltage and/or lower capacity station batteries are even less researched. As a result, a series of arc-flash tests were performed at the Dolan Technology Center of American Electric Power (AEP) utilizing two 125 Vdc batteries with rated capacities of 100 and 150 Ah. For these tests, working distance and gap width were used as independent variables. Upon the conclusion of testing, various relationships were analyzed to generate a predictive model for incident energy. This model serves as a compilation of the empirical data collected during testing and will contribute to future research efforts to better understand dc arc-flash incidents from station batteries.