TCC Evaluation Method for Evaluating Arc Flash and Arc Blast Hazard at Low Voltages and First-Degree Burns

Traditionally, arc flash evaluations have had little to no methodologies for evaluation or literature below the Category 1 (CAT 1), which is $4 \mathrm{cal} / \mathrm{cm}^{2}$, or even below $1.2 \mathrm{cal} / \mathrm{cm}^{2}$, which is a second-degree burn. This lower level of the arc flash hazard has been treated as a survivable/curable range, since it is mainly a region of 250 VAC and 130 VDC and below. Historical are flash research, calculation theory and PPE (Personal Protected Equipment) development has been on the highest levels of arc flash above 1.2 or $4 \mathrm{cal} / \mathrm{cm}^{2}$. This excellent work in labs and theory has produced the recent IEEE 1584-2018 formulation for estimating arc flash levels. However, arc flash events lower than CAT 1 can still produce very damaging results to the human body, not necessarily to the PPE covered area of the body, but to those portions that may not always be covered, such as the bare skin of the face. Therefore, there is a vulnerability to serious damage to any bare skin sites. To address this concern the author has used the TCC (Time-Current-Coordination) arc flash evaluation method to provide a visual and tabular plotting of this vulnerability. The paper will address not only how a second-degree burn can occur at these low voltage levels but, for the first time in publication the plotting on TCCs will consider a first-degree burn as well. Also introduced will be the concept of a “minor arc blast” and its possible codamaging to the skin, which can be far more damaging than the short-lived arc flash itself. The paper presents this TCC method/technique to examine the arc flash and arc blast at low voltages and provides a real field example of the damage it caused to an electrical worker from an actual event that had both an arc flash and a following minor arc blast.