Change Summary

• Article 712 “Direct Current Microgrids” was added to the 2017 NEC for a power distribution system consisting of more than one interconnected dc power sources, supplying dc–dc converters(s), dc loads(s), and/or ac loads(s) powered by dc–ac inverters(s).
  Direct Current Microgrids is a specialized area of work for electrical professionals and beyond the scope of this Captain Code document. However we provide this brief mention here to inform our readers of this emerging technology. If you are involved in this work we recommend reading article 712 in its entirety in NEC 70.

Expert Analysis

A dc microgrid is defined as a power distribution system consisting of more than one interconnected dc power source, supplying dc–dc converters(s), dc loads(s), and/or ac loads(s) powered by dc–ac inverters(s). A dc microgrid is typically not directly connected to an ac primary source of electricity, but some dc microgrids interconnect via one or more dc–ac bidirectional converters or dc–ac inverters. DC microgrids allow the direct utilization of power from dc sources to dc loads such as LED lighting, communications equipment, computers, variable-speed motor drives, etc. Direct utilization of dc, whether generated by PV systems, fuel cells or other means (without intervening dc–ac and ac–dc conversion steps) leads to higher efficiencies and potentially smaller and lower-cost equipment than accoupled methods.