ARC flash studies: An internship with Fortesque Metals Group Limited

A significant safety risk to electrical personnel working on an energised switchboard is the hazard of exposure to arc flash, which has gained increasing attention over the past decade. Although reported arc flash injuries are infrequent compared to other electrical injuries, especially electric shock, the very high costs associated with these arc flash injuries make them one of the most important categories to avoid in an industrial workplace. The main objective of this project is to conduct arc flash studies for switchboards installed at Fortescue’s Solomon Hub to quantify the existing arc flash hazard posed by this type of equipment. The aim of the study is to find feasible solutions to reduce arc flash incident energy to less than 8 cal/cm2 and to provide appropriate arc flash PPE recommendations. Switchboards with voltage levels of 0.4kV, 0.69kV, 6.6kV, 11kV and 33kV were investigated. The arc flash calculations were conducted using the IEEE 1584-2002 Standard, IEEE Guide for Performing Arc-Flash Hazard Calculations. The study found that many switchboards have dangerous incident energy levels that must be reduced, in order to allow energised work on the equipment. To mitigate the hazard, three simple solutions were proposed: optimise protection settings, install maintenance switches and remote operation. Firstly, optimising protection settings is the least expensive solution to reduce the operating time of protection devices, and hence limit arc flash incident energy exposure. Secondly, where a permanent setting will violate the grading requirement of the system, then installing maintenance switches is proposed. Thirdly, where the first two strategies cannot be implemented because they will violate the grading requirement of the system, then remote operation is proposed. This will eliminate the arc flash hazard because personnel will operate the equipment outside the arc flash boundary. If the recommendations of this study are implemented, the arc flash incident energy of the switchboards will significantly reduce to not greater than 8 cal/cm2. The implications are improved safety for personnel, given that energy levels on many switchboards currently pose a significantly higher arc flash hazard