Using a microprocessor-based instrument to predict the incident energy from arc-flash hazards

With better understanding of arc flashes, the electrical safety industry continues to develop new safety procedures for electrical workspaces. To assess the potential arc hazards of a workspace, workers must rely on engineering fault studies to provide vital fault-current data. An instrument, based on a network impedance analyzer, determines the maximum flash-arc incident-energy exposure at a worksite within a few seconds. The digital analyzer measures the power system source impedance, X/R ratio, and the system voltage to predict the bolted fault current and incident energy, while the power distribution system is energized and in normal operation. The instrument computes the incident energy for standard electrical workspaces of an open-air arc and an enclosed box with one open side. Experiments have been conducted to verify the accuracy of the impedance and X/R ratio measurements.