Arc Flash Hazard Assessment Worksheet for Low-Fault-Current Microgrids (IEEE 1584-2018 Adapted)

Arc flash hazard assessment in low-fault-current microgrids presents unique challenges because inverters—unlike synchronous generators or transformers—do not inherently supply high-magnitude, sustained fault currents. Instead, their fault contribution is constrained by semiconductor limits (e.g., 1.5–2.0 per-unit peak current), governed by embedded protection logic, and shaped by control-mode transitions (e.g., grid-following to grid-forming during islanding). The IEEE 1584-2018 standard, while robust for utility-scale systems, assumes bolted fault currents that decay predictably and ignores inverter-specific dynamics such as current-limiting algorithms, DC-link voltage sag effects, and variable clearing times due to adaptive relaying. This adapted worksheet bridges that gap by integrating empirical inverter fault-current profiles, time-current characteristic (TCC) overlays for inverter-integrated protection, and a hybrid arc-flash modeling approach: it uses IEEE 1584’s empirical equations where applicable but substitutes inverter-specific arcing current (I_arc) and clearing time (t_clear) inputs derived from manufacturer data, hardware-in-the-loop (HIL) test results, or validated simulation (e.g., PSCAD/EMTP). Furthermore, the worksheet includes sensitivity analysis tabs to quantify uncertainty from variables like grounding configuration (high-resistance vs. solid), arc gap variability under low-current conditions, and the impact of distributed energy resource (DER) dispatch states on available fault current—enabling risk-informed maintenance planning and PPE selection even when nominal fault currents fall below conventional protective device pickup thresholds.