Electric power systems design: The NEC and the IEC approach

The purpose of this paper is to compare the techniques and results obtained when a general industrial or commercial building power electrical system is prepared using the United States National Electrical Code© (NEC©) and the International Electrotechnical Commission (IEC) Standards. The final design offers the reader the possibility of making an initial comparison and analyzation of the two methods based on their overall effectiveness (sizing, protection, co-ordination of protective devices with components etc.), safety and cost. In order to make such a comparison, a specific example was developed and limited in detail to avoid complexity in this study. The power source selected is a delta-wye utility supplied transformer feeding various load groups such as lighting and motor circuits (possibly through associated transformers). Relevant NE Code references, IEC standards, and appropriate justifications are made at various points. Since this paper is for comparison purposes only, arbitrary values are selected to illustrate various concepts. In a “real life” design, guidance from the Color Book series of the Institute of Electrical and Electronic Engineers (IEEE), is strongly recommended