Protection planning and system design to reduce arc flash incident energy in a multi-voltage level distribution system to 8 CAL/CM2 (HRC 2) or less – part I: Methodology

The industry is heading towards innovations in the electrical systems designs, equipment and protection to limit the arc flash hazard. The paper demonstrates that in a multi-voltage level (medium and low-voltages) distribution system the incident energy can be reduced to 8 cal/cm², or even less, (Hazard risk category, HRC2), so that a PPE outfit of greater than 2 is not required. This is achieved with the current state of the art equipment and protective devices. This paper is in two parts, part I, methodology and Part II, analysis. There are variations in the calculation results depending upon the calculation methods. A new method for calculation of energy accumulation to account for decaying nature of short-circuits currents is presented.