Arc-flash incident reconstruction.

§1Scope of work

The work begins with a sealed scene visit, typically within forty-eight hours of the incident. The most useful evidence is perishable: the worker’s PPE garment, the working position relative to the arc source, the burned label or door of the equipment, the position of any circuit breaker auxiliary contacts at the time, and the upstream protection’s trip records. By the time a litigation matter is opened months later, half of this is typically gone. R-02 work conducted from cold-file evidence is materially less reliable than R-02 work conducted from a sealed scene; we are explicit on that in every report.

R-02 is the firm’s second most active Protocol after R-01. Pennsylvania, Ohio, and western New York have a dense population of pre-2002 480 V industrial switchgear, much of it installed under the 1996 and 1999 NEC and predating the 2002 introduction of arc-flash labeling requirements in NEC 110.16. Where labels are present, we read them against calculated incident energy. Where labels are absent, we calculate from first principles and report the result against what the worker’s clothing system was rated for.

R-02 work is also retained by employers conducting their own pre-incident review under 29 CFR 1910.132(d) hazard assessment requirements. This is the only R-02 work the firm undertakes on a non-incident basis; the methodology is identical to the post-incident protocol minus the scene-evidence step.

§2Reconstruction methodology

The first reconstruction question is: what was the available short-circuit current at the equipment terminal? The available short-circuit current sets the floor on which the IEEE 1584 calculation rests, and getting it wrong by a factor of two — easy to do on a building whose original utility-supplied infrastructure summary is twenty years old — invalidates the rest of the file.

We re-derive the available short-circuit current at the failure terminal from utility-supplied secondary-side values updated to the date of the incident, transformer impedance values read from the transformer nameplate or pulled from the manufacturer’s archive (typically Eaton, ABB, Siemens, or Schneider Electric Square D), and the impedance contribution of the conductor from the source to the terminal. The calculation engine is typically SKM PowerTools for industrial single-line studies and ETAP where a third-party study already exists in that format; we do not deviate without reason. Hand-calculated check is performed on every file under the IEEE 1584-2018 Annex B reference equations.

The second reconstruction question is the duration of the arc. Upstream protection clearing time governs the duration, and the relevant evidence is the upstream device’s trip record where logged, the device’s observed condition (operated/closed; reset/un-reset; melted fuse element retained), and the manufacturer’s published time-current curve. We retain a permanent archive of TCCs for the major manufacturers shipping to the Lake Erie corridor since the 1980s; very old switchgear can be looked up in the Eaton Cutler-Hammer historical archive or in the Bureau of Reclamation distribution-equipment archive when the device predates published TCCs.

§3Incident-energy calculation

IEEE 1584-2018 provides the calculation framework for arc current and incident energy as a function of bolted fault current, system voltage, gap distance, electrode configuration, equipment enclosure dimensions, and working distance. The 2018 edition expanded the empirical model significantly from the 2002 first edition, and a great many installed arc-flash labels in the field are still calculated to 2002 values. Recomputing under 2018 — especially for VCB (vertical conductors in a box), VCBB (vertical conductors in a box with barrier), HCB (horizontal conductors in a box), VOA (vertical open in air), and HOA configurations — frequently moves the incident energy by 30% or more.

The 2018 expansion is the firm’s single most-cited finding in arc-flash matters. Where the installed label was calculated under the 2002 edition at, say, 8.2 cal/cm² at 18″ working distance, the same equipment recalculated under the 2018 edition at the same working distance frequently reports 12 cal/cm² or higher — placing the worker’s clothing system one PPE category short of what the actual hazard required. OSHA has not (as of 2026) made the 2018 IEEE edition retroactively mandatory for installed labels, but in litigation the plaintiff’s expert can be expected to cite it, and a defense expert who has not recalculated under 2018 is a defense expert who has missed the most important question on the file.

§4PPE forensics

The injured worker’s clothing system is the second leg of the reconstruction. PPE forensics is conducted under ASTM F1959 garment energy testing and ASTM F2178 face-protection testing, with the garment examined in a controlled environment for the burn-through pattern, the percentage of garment area exposed to thermal damage, the presence or absence of breakopen at the seams or zippers, and the labels stitched into the garment that report the manufacturer’s arc-rating (ATPV or EBT) at time of manufacture.

The relevant comparison is between the worker’s clothing system’s ATPV (Arc Thermal Performance Value) and the incident energy at the working distance at which the worker stood. Where the ATPV is greater than the incident energy, the clothing system was adequate. Where the ATPV is less than the incident energy, the clothing system was inadequate at the working distance documented, and the next question is whether the working distance was the one called out on the installed label or a different one. NFPA 70E §130 categorizes PPE by ATPV against incident energy, not by manufacturer or by category alone; we read it that way.

The firm subcontracts the actual garment testing where necessary to a NVLAP-accredited textile lab (typically Intertek in Cortland, NY, or UL Solutions in Northbrook). Our engineers do not perform ASTM F1959 testing in-house; we are not a textile laboratory. The lab’s report becomes a sealed exhibit on the file.

§5Working distance & the common error

The most common finding on R-02 matters is a working-distance discrepancy between the installed arc-flash label and the worker’s actual position at the time of the incident. The IEEE 1584 calculation reports incident energy at a specified working distance — typically 18 inches for 480 V Class equipment, 36 inches for 5 kV equipment, and 48 inches or more for 15 kV — and the installed label reports the cal/cm² at that distance. A worker performing voltage testing on a 480 V cubicle with a Fluke 87V at the lead tip is reasonably close to 18 inches from the live parts. A worker pulling a Cutler-Hammer Magnum DS drawout breaker out of its compartment is closer to 36 inches at the breaker frame and substantially farther at the bus stab. The applicable incident energy depends on which task the worker was performing at the moment of arc initiation, and the installed label can only be one of those distances.

CF-2025-104 in this issue (the Erie foundry arc-flash, featured at its dossier page) is a clear example. The installed label reported 8.4 cal/cm² at 18 inches working distance; the calculation was unimpeachable at that distance. The injured worker was performing infrared scanning through an open-door cubicle at approximately 26–30 inches from the bus stab. Recalculated at 28 inches, the actual incident energy was 4.9 cal/cm² — the worker’s 8 cal/cm² Category 2 system was adequate. The injury, when finally reconstructed, traced to a different mechanism: ignition of a contaminant on the worker’s glove from the IR window’s ZnSe coating residue, not to incident-energy exposure exceeding the clothing system. The matter settled.

§6Deliverable & fee

The R-02 deliverable is a sealed PE report with: scope statement; available short-circuit current calculation with utility-supplied inputs and date; arc current and incident-energy calculation under IEEE 1584-2018 at the documented working distance and at any alternate distances called for by the matter; arc-duration analysis with upstream-protection time-current curve overlay; PPE forensic report (or sub-laboratory’s sealed report) where the garment is available; finding on whether the worker’s clothing system was adequate for the actual incident energy. The fee band is $8,500 to $32,000.

Engagement terms are at the Engage page. R-02 matters frequently cross-reference R-06 (grounding/bonding) where the arc origin involves an objectionable current path; the firm routinely opens both files in parallel when warranted.

§7References