Arc flash evaluation and hazard mitigation for the Colorado School of Mines electrical power distribution system

An arc flash is the release of electrical energy during an arcing fault, which dissipates in the form of heat energy, intense light, blast pressure, severe sound waves, electromagnetic radiation, and toxic gases. The thermal energy, concussive forces, and flying debris can pose serious threats to the safety of personnel working in close proximity to electrical equipment. In order to identify the severity of an arc flash hazard at the Colorado School of Mines (CSM), an arc flash hazard evaluation of the electrical power distribution system has been conducted. The arc flash analysis has been performed in accordance with NFPA 70E: Standard for Electrical Safety in the Workplace, and IEEE 1584: Guide for Performing Arc Flash Hazard Calculations. The analysis of the existing system configuration has revealed that many locations on the CSM campus are in the “dangerous” arc flash hazard category, and consequently work cannot be performed on energized equipment at these locations. With an understanding of the thermal energy available, design recommendations, including the selection and coordination of fuses and circuit breakers, were investigated to reduce the severity of arc flash events. Implementation of the selected protective devices can decrease the incident energy levels of CSM locations and eliminate any instances of “dangerous” hazard risk categories. Other hazard mitigation considerations include increasing the working distance, and utilizing arc suppression blankets while performing maintenance. In addition, electrician training to promote safe work practices is strongly encouraged.