The 2012 version of the National Electrical Safety Code (NESC) has significant changes for distribution arc flash on secondary networks below 1000 V. EPRI research has been targeted to address those changes, particularly at 480 volts for spot networks and self-contained meters.
The 2012 NESC requires an analysis, and many spot networks can have well over 100 cal/cm2 of exposure. Research and analysis have shown that work can still be done with a combination of proper arc flash suits and work practices. In addition to deenergizing the primary side, there are other promising options. Utilities can use this information to improve their arc flash programs for 480-volt spot networks.
Exploratory arc flash tests were performed on meter sockets, a current transformer (CT) cabinet, and an overhead scenario to evaluate the thresholds of incident energy given in the NESC's new table 410-1. For the CT cabinet and the overhead work, the tests validated the NESC thresholds.
For self-contained meter bases, results showed that higher rated meter sockets, or multi-socket units with significant bus bars, can have significantly higher incident energies than those given in the NESC table. Utilities can use this information to adjust their arc flash programs to better protect workers working on this type of unit.
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