The Effects of System Grounding, Bus Insulation and Probability on Arc Flash Hazard Reduction - Part 2: Testing

This paper provides a follow-up to the paper, The Effects of System Grounding, Bus Insulation and Probability on Arc Flash Hazard Reduction - The Missing Links. [1] In that paper, system grounding and bus insulation were considered a means of reducing the probability of an arc flash incident by approximately two orders of magnitude. In September 2013, additional testing was conducted on a low voltage motor control center with the expectation that engineering enhancements such as insulated vertical bus, high resistance grounding, and other techniques, could be implemented to further reduce the probability of an arc flash incident. The testing performed was with faults initiated in locations typically found in operating petrochemical facilities, in low voltage motor control centers, with the starter unit door open. This paper discusses the findings of testing on real-world electrical equipment in an effort to further understand and minimize the probability of an arc flash incident. The paper reviews the physics of the arcing fault and how ignition wire, geometry, and the number of anode/cathode pairs all contribute to arcing fault energy and personnel exposure.