Arc Flash Study

Maximum fault (Scenario 1) assumes all sources are online and tie breakers are closed, giving the highest bolted fault current. This drives the incident energy upper bound and determines PPE requirements. Minimum fault (Scenario 2) assumes only the utility is online at minimum contribution and no other sources are active — this may result in longer clearing times and potentially higher incident energy despite lower fault current. Typical (Scenario 3) represents the normal operating configuration with intermediate source contributions. All three are required because NFPA 70E and IEEE 1584 both require the study to bound the hazard range, not just report a single point estimate.

The 2-second rule (IEEE 1584 §4.11) allows assuming the arc self-extinguishes within 2 seconds — reducing incident energy. It applies to freely burning arcs in air. It does NOT apply in confined spaces such as inside a Power Conversion System (PCS) enclosure, where arc cooling is limited and the arc may persist beyond 2 seconds regardless of protective device timing.

No. Individual equipment labels are required per NFPA 70E. Each bus, switchgear compartment, or MCC section should have its own label reflecting the actual calculated incident energy for that location. Exception: PV Load Break Disconnectors (LBDs) and combiner boxes on the DC side may use a worst-case blanket label because their incident energy is relatively uniform across the array and individual labeling may be impractical at scale.

Use IEEE 1584-2018 for all AC sources and system configurations. Use the DC Paukert method exclusively for the PV array DC side — it is not valid for AC. The DC arc flash hazard from PV modules and combiner boxes must be assessed separately, and all DC sources must be included in the LOTO procedure referenced on high-energy (>40 cal/cm²) labels. The two hazard domains are independent and cannot be combined into a single incident energy value.

IEEE 1584-2018 is validated for voltages up to 15 kV. For equipment above 15 kV, the standard notes that ARCPRO™ software or the ETAP ArcFault Module should be used for final study determination. These tools use the IEEE 1584-2018 framework extended with additional electrode configuration data and empirical validation for higher voltages. FrameAI can provide preliminary estimates for >15 kV systems, but a qualified engineer should validate with industry-standard software before finalizing labels.

You need the bolted three-phase fault current (Ibf) at each bus for your three scenarios. Maximum scenario: Ibf_max from the maximum fault study with all sources online. Minimum scenario: Ibf_min from the minimum fault study with only utility contribution. Typical scenario: Ibf_typ from your normal operating configuration. You also need the upstream protective device clearing time at each bus — read from the time-current characteristic (TCC) curve of the upstream breaker. If you do not have a short-circuit study yet, use FrameAI's free IEC 60909 short-circuit calculator.

After running the study, enter your equipment name and study date in the Labels section and click "Send Labels." The label set (JSON) is emailed to you and contains: Danger/Warning header per ANSI Z535, Arc Flash and Shock Hazard list, incident energy + working distance, arc flash boundary, nominal voltage, equipment name, study date, and the note "weather + UV resistant, minimum 5-year life." Labels should be printed on durable material and affixed to each piece of equipment per NFPA 70E §130.5.