DC Arc Hazard Mitigation Design at a Nuclear Research Facility

Although potential arc heat and blast energy from dc sources may be significant, the risk assessment for exposure to dc energy sources is often not performed because the requirement to do so is not understood. Making the task of quantifying dc arc energies more intimidating is that the professional engineer often assumes liability for any errors or omissions that may result in injury, or worse. Compounding the issue even further is that the analysis work is often based on tools, methods, and verifications for dc arc heat and blast energies that are incomplete and immature. Explained here is one approach taken to perform an arc heat and blast analysis for a research facility, specifically a concentrated load supplied by eight 1-MW silicon-controlled rectifiers regulating +/-300 Vdc outputs to tightly arranged terminations at a load. During the course of the research, the connections were to be reconfigured, followed by a planned retuning of the regulated dc output using handheld multimeters at the load terminations, without wearing personal protective equipment. After assessing the risk, the research engineers were easily convinced that a full analysis is needed to be performed with risk mitigation design.