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This paper demonstrates that, in a multi-voltage-level (medium and low voltages) distribution system, the incident energy can be reduced to 8 cal/cm2 (hazard risk category 2) or even less, so that a personal protective equipment outfit of greater than two is not required. This is achieved with the current state-of-the-art equipment and protective devices. It is recognized that, in the existing distribution systems, not specifically designed with this objective, it may not be possible to reduce the arc-Flash hazard to this low level, unless major changes in the system design and protection are made. A typical industrial distribution system is analyzed, and tables and time-coordination plots are provided to support the analysis. Unit protection schemes and practical guidelines for arc-Flash reduction are provided. The methodology of IEEE 1584 is used for the analyses. Reducing HRC also reduces the fault damage to the equipment.
Date of Publication: Jan.-Feb. 2011